Careercup Top 150 Questions

Cracking the Technical Interview by Gayle Laakmann, CareerCup. com 150 Technical Interview Questions and Solutions, written by experts. PLUS: » » » Behind the scenes look at Google Microsoft, Amazon and Yahoo interviews. Interview War Stories: the view from the other side. Advice on how to approach 24 types of interview questions. Copyright Information Copyright 2009 by Gayle Laakmann All rights reserved exclusively for XU-bp75mklu3ja@checkout. google. com www. careercup. com Table of Contents Introduction Practice Interviews. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 The Microsoft Interview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 The Amazon Interview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 The Google Interview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 The Yahoo Interview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Interview War Stories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Interview Questions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 Chapter 12 Chapter 13 Chapter 14 Applied Mathematics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Arrays & Hash Tables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Bit Manipulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Brain Teasers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 C / C++ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Counting and Combinatorics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Database. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Debugging Existing Code. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Games . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Java. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Large Scale & Memory Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Linked Lists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Low Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Matrix. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 4 © 2009 CAREERCUP exclusively for XU-bp75mklu3ja@checkout. google. com Table of Contents

Chapter 15 Chapter 16 Chapter 17 Chapter 18 Chapter 19 Chapter 20 Chapter 21 Chapter 22 Chapter 23 Chapter 24 Networking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 Object Oriented Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 Probability and Randomness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 Software and System Design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Sorting and Searching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 Stacks and Queues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 Strings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 Threads And Locks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Trees and Graphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 © 2009 CAREERCUP 5 Practice Interviews Studying helps, but nothing can prepare you like the real thing. Each CareerCup interviewer has given over a hundred interviews at Google, Microsoft, or Amazon. To nail your interview, sit down with a trained interviewer and get their experienced feedback. See www. careercup. om/interview for more details. One Hour Interview with Real Interviewers Our interviewers will give you a real interview, just like you’d get at Google, Microsoft or Amazon. We’ll test you on the same types of questions that they do. We’ll grade you the same way they do. How can we do this? We’ve done over 100 interviews each for these companies. We’ve screened resumes. We’ve been part of their hiring committees. We know what they want. We’ll Also Give You... » » » » » An . mp3 recording of your interview. Feedback on where you shined and where you struggled. Specific suggestions on how to improve.

Instructions on how to approach tough problems Lessons on what interviewers look for in your code. A Typical Interview A typical interview includes a brief discussion of your resume and one or more technical questions. Each interview will do coding via a shared document. When the interview is completed, we’ll give you immediate feedback on how you did while it’s still fresh in your mind. Later that day, you’ll receive an mp3 of the interview to refresh your memory. Schedule Your Interview Today! See http://www. careercup. com/interview for pricing and details! 6 © 2009 CAREERCUP xclusively for XU-bp75mklu3ja@checkout. google. com The Microsoft Interview Microsoft wants smart people. Geeks. People who are passionate about technology. You probably won’t be tested on the ins and outs of C++ APIs, but you will be expected to write code on the board. In a typical interview, you’ll show up at Microsoft at some time in the morning and fill out initial paper work. You’ll have a short interview with a recruiter where he or she will give you a sample question. Be nice to your recruiters; while they may not evaluate your technical skills in depth, they can fight for you to be hired - or not.

Throughout the day, you’ll move around from interviewer to interviewer, visiting each one in their office. Use this time to look around and get a feel for what the team culture. Interviewers are not allowed to share their feedback on you with other interviewers, due to concerns of bias. Nonetheless, many sources indicate that some feedback is shared. When you complete your interviews with a team, you might speak with a hiring manager. If so, that’s a great sign! It likely means that you passed the interviews with a particular team. It’s now down to the hiring manDefinitely Prepare: ager’s decision.

You might get a decision that day, or it might be a week. After one week of no word from HR, send them a friendly email asking for a status update. “Why do you want to work for Microsoft? ” In this question, Microsoft wants to see that you’re passionate about technology. A great answer might be, “I’ve been using Microsoft software as long as I can remember, and I’m really impressed at how Microsoft creates manages to create a product that is universally excellent. For example, I’ve been using Visual Studio recently to learn game programming, and it’s APIs are excellent. ” Note how this shows a passion for technology!

What’s Unique: You’ll only reach the hiring manager if you’ve done well, but if you do, that’s a great sign! XU-bp75mklu3ja@checkout. google. com © 2009 CAREERCUP 7 The Amazon Interview Amazon’s recruiting process usually begins with one or two phone screens in which you interview with a specific team. The engineer who interviews you will usually ask you to write simple code and read it aloud on the phone. They will ask a broad set of questions to explore what areas of technology you’re familiar with. Next, you fly to Seattle for four or five interviews with one or two teams which have selected you based on your resume and phone interviews.

You will have to code on a whiteboard, and some interviewers will stress other skills. Interviewers are each assigned a specific area to probe and may seem very different from each other. They can not see other feedback until they have submitted their own and they are discouraged from discussing it until the hiring meeting. Amazon’s “bar raiser” interviewer is charged with keeping the interview bar high. They attend special training and will interview candidates outside their group in order to balance out the group itself.

If one interview seems significantly harder and different, that’s most likely the bar raiser. This person has both significant experience with interviews Definitely Prepare: and veto power in the hiring decision. You Amazon is a web-based company, and will meet with your recruiter at the end of the day. that means that they care about scale. Once your interviewers have entered their feedback, they will meet to discuss it. They will be the people making the hiring decision. While Amazon’s recruiters are excellent at following up with candidates, occasionally there are delays.

If you haven’t heard from Amazon within a week, we recommend a friendly email. Make sure you prepare questions in “Large Scale. ” You don’t need a background in distributed systems to answer these questions. Just answer the question for one system and then think, how does your solution change with multiple computers? Additionally, Amazon tends to ask a lot of questions that are based in mathematics and randomness. What’s Unique: The Bar Raiser, who is brought in from a different team to keep the bar high. 8 © 2009 CAREERCUP exclusively for XU-bp75mklu3ja@checkout. google. com The Google Interview

There are many scary stories floating around about Google interviews, but it’s mostly just that: stories. The interview is not terribly different from Microsoft’s or Amazon’s. However, because Google HR can be a little disorganized, we recommend being proactive in communication. A Google engineer performs the first phone screen, so expect tough technical questions. On your onsite interview, you’ll interview with four to six people, one of whom will be a lunch interviewer. Interviewer feedback is kept confidential from the other interviewers, so you can be assured that you enter each interview with blank slate.

Your lunch interviewer doesn’t submit feedback, so this is a great opportunity to ask honest questions. Written feedback is submitted to a hiring committee of engineers to make a hire/no-hire recommendation. Feedback is typically broken down into four categories (Analytical Ability, Coding, Experience and Communication) and you are given a score from 1. 0 to 4. 0 overall. The hiring committee understands that you can’t be expected to excel in every interview, but if multiple people raise the same red flag (arrogance, poor coding skills, etc), that can disqualify you.

A hiring committee typically wants to see one interviewer who is an “enthusiastic endorser. ” In other words, a packet with scores of 3. 6, 3. 1, 3. 1 and 2. 6 is better than all 3. 1’s. Your phone screen is usually not a factor in the final decision. The Google hiring process can be slow. If you don’t hear back within one week, politely ask your recruiter for an update. A lack of response says nothing about your performance. Definitely Prepare: As a web-based company, Google cares about how to design scalable system. So, make sure you prepare question from “Large Scale. Additionally, many Google interviewers will ask questions involving bit shifting and Bit Manipulation, so please brush up on these questions. What’s Different: Your interviewers do not make the hiring decision. Rather, they enter feedback which is passed to a hiring committee. The hiring committee recommends a decision which can be—though rarely is—rejected by Google executives. XU-bp75mklu3ja@checkout. google. com © 2009 CAREERCUP 9 The Yahoo Interview Resume Selection & Screening: While Yahoo tends to only recruit at the top 10 – 20 schools, other candidates can still get interviewed through

Yahoo’s job board (or – better yet – if they can get an internal referral). If you’re one of the lucky ones selected, your interview process will start off with a phone screen. Your phone screen will be with a senior employee (tech lead, manager, etc). Onsite Interview: You will typically interview with 6 – 7 people on the same team for 45 minutes each. Each interviewer will have an area of focus. For example, one interviewer might focus on databases, while another interviewer might focus on your understanding of computer architecture.

Interviews will often be composed as follows: 5 minutes: General conversation. Tell me about yourself, your projects, etc. 20 minutes: Coding question. For example, implement merge sort. 20 minutes: System design. For example, design a large distributed cache. These questions will often focus on an area from your past experience or on something your interviewer is curDefinitely Prepare: rently working on. Decision: At the end of the day, you will likely meet with a Program Manager or someone else for a general conversation (product demos, concerns about the company, your competing offers, etc).

Meanwhile, your interviewers will discuss your performance and attempt to come to a decision. The hiring manager has the ultimate say and will weigh the positive feedback against the negative. If you have done well, you will often get a decision that day, but this is not always the case. There can be many reasons that you might not be told for several days – for example, the team may feel it needs to interview several other people. Yahoo, almost as a rule, asks questions about system design, so make sure you prepare that. They want to know that you can not only write code, but that you can design software.

Don’t worry if you don’t have a background in this - you can still reason your way through it! What’s Unique: Your phone interview will likely be performed by someone with more influence, such as a hiring manager. Yahoo is also unusual in that it often gives a decision (if you’re hired) on the same day. Your interviewers will discuss your performance while you meet with a final interviewer. 10 © 2009 CAREERCUP exclusively for XU-bp75mklu3ja@checkout. google. com Interview War Stories The View from the Other Side of the Front, by Peter Bailey

For the eager candidate getting ready for a big job interview, Cracking the Technical Interview is an invaluable reference, containing excellent coaching and practice material that gives you an inside edge on the interview process. However, as you go over your old data structures textbook and drill yourself with homemade discrete math flash cards, don’t make the mistake of thinking of the interview as a kind of high-pressure game show – that if you just give all the right answers to the tech questions, you too can win a shiny new career (this week, on Who Wants to be a Software Engineer? While the technical questions on computer science obviously are very important, the most important interview question is not covered in this guidebook. In fact, it’s often the single most important question in your interviewers’ minds as they grill you in that little room. Despite the questions on polymorphism and heaps and virtual machines, the question they really want an answer to is ... Would I have a beer with this guy? Don’t look at me like that, I’m serious! Well, I may be embellishing a little, but hear me out.

The point I’m trying to make is that interviewers, especially those that you might work with, are probably just as anxious as you are. Nonsense, you say, as a nervous young professional, checking your pants for lint while you bite your fingernails, waiting for the interview team to show up in the front lobby. After all, this is the big leagues, and these guys are just waiting for you to slip up so they can rip you apart, laugh at your shriveled corpse, and grind your career dreams to dust beneath the heels of their boots. Right? Just like pledge week, back in freshman year?

Right? Hmmm? Nothing could be further from the truth. The team of developers and managers interviewing you have their own tasks and projects waiting for them, back at their own desks. Believe me, they’re hoping that every interview is going to be the last one. They’d rather be doing anything else. There might be a batch of upcoming projects looming on their calendar, and they need more manpower if they’re going to even have a prayer of making their deadline. But the last guy the agency sent over was a complete flake who railed about Microsoft’s evil for half an hour.

And the one before that couldn’t code his way out of a wet paper bag without using copy-and-paste. Sheesh, they think, where is HR getting these guys? How hard can it be to hire one lousy person? While they may not literally be asking themselves “Would I have a beer with this guy (or gal)”, they are looking to see how well you would fit in with the team, and how you would affect team chemistry. If they hire you, you’re all going to be spending a lot of time together for 11 © 2009 CAREERCUP exclusively for XU-bp75mklu3ja@checkout. google. com Interview War Stories he next few months or years, and they want to know that they can rely on you – and maybe even come to consider you a friend and colleague. They want to know that they can depend on you. And as tempting as it might be to them to just settle and hire the next person who comes along, they know better. In many companies, particularly large U. S. companies, it’s harder to fire somebody than it is to hire somebody. (Welcome to the US: Land of Lawsuits! ) If they hire a dud, they’re stuck with them. That person might be unproductive or, even worse, a drain on the team’s productivity.

So they keep interviewing, until they find the right person. They know that it’s better to reject a good candidate than hire a bad one. Some of those interviews are real doozies. Once you’ve interviewed long enough, you build up a repertoire of horror stories. War stories, of candidates who looked promising on paper until the interviews went terribly, terribly wrong. These war stories are not only humorous – they’re also instructive. Names have been changed to protect the innocent – or downright ridiculous. zyxwvutsrqponmlkjihgfedcba ZYXWVUTSRQPONMLKJIHGFEDCBA spwXU-bp75mklu3ja@checkout. google. comkjlslen 0987654321+_=-)(*&^%$#@! ~[]{};’:”,. /? ABCDEZYXW abcdeyxw asdsasdFGJwRXGs75rpqR3oFWHMJHp-RQ. L--LqJ. H-rsdkktNNsasdf XU-bp75mklu3ja@checkout. google. com XU-bp75mklu3ja@checkout. google. com © 2009 CAREERCUP 12 Interview War Stories Pop Divas Need Not Apply Leonard was a very promising C++ coder, three years out of college, with a solid work history and an impressive skill set. He proved on the phone screen that he was above-average technically, and so he was invited in for an interview. We needed a savvy C++ person to work on a piece of middleware that interfaced with our database, and Leonard seemed like a sure fit.

However, once we started talking to him, things went south in a hurry. He spent most of the interview criticizing every tool and platform that we questioned him on. We used SQL Server as our database? Puhleease. We were planning to switch to Oracle soon, right? What’s that? Our team used Tool A to do all our coding in? Unacceptable. He used Tool B, and only Tool B, and after he was hired, we’d all have to switch to Tool B. And we’d have to switch to Java, because he really wanted to work with Java, despite the fact that 75 percent of the codebase would have to be rewritten.

We’d thank him later. And oh, by the way, he wouldn’t be making any meetings before ten o’clock. Needless to say, we encouraged Leonard to seek opportunities elsewhere. It wasn’t that his ideas were bad – in fact, he was “technically” right about many things, and his (strong) opinions were all backed with solid fact and sound reason (except for the ten o’clock thing – we think he may have just been making a “power play”. ) But it was obvious that, if hired, Leonard wasn’t going to play well with others – he would have been toxic kryptonite for team chemistry.

He actually managed to offend two of the team members during the forty-five minutes of his interview. Leonard also made the mistake of assuming that Code Purity and Algorithm Beauty were always more important than a business deadline. In the real world, there are always compromises to be made, and knowing how to work with the business analysts is just as important as knowing how to refactor a blob of code. If Leonard would not have gotten along with other IT people, he definitely wouldn’t have gotten along with the business folks. Maybe you can get away ith hiring a Leonard if he’s one of the best ten coders in the world (he wasn’t). But he was the classic failure example for the “Would you have a beer with this guy? ” test. 13 © 2009 CAREERCUP exclusively for XU-bp75mklu3ja@checkout. google. com Interview War Stories What We Have Here is Failure to Communicate Trisha was a mid-level Java developer with a solid history of middleware and JSP work on her resume. Since she was local, we invited her in for an interview without a phone screen. When we started asking her questions, it quickly became obvious that Trisha was a woman of few words.

Her answers were short and often composed of “yes/no” responses, even to questions that were meant to start a dialog. Once she did start opening up, I still wasn’t sure she was actually talking. I saw her lips moving, and heard mumbling sounds coming out, but it wasn’t anything that sounded like English. I’m not sure if Trisha was nervous or just shy, but either way, I had to ask her numerous times to repeat herself. Now I was the one getting nervous! I didn’t want to be the guy who “ruined” the interview, so I pulled back on my questions. The other folks in the room and I exchanged uneasy glances.

We felt like we were on a Seinfeld episode. It was almost impossible to understand Trisha, and when she did speak up, her halting, uncertain, confused speech patterns made us feel more like code breakers than interviewers. I am not exaggerating to say that I did not understand a single answer she gave during the interview. Knowing, alone, isn’t good enough. You’re going to be talking with other technical people, and you’re going to be talking to customers, and sales reps, and Betty from Marketing. You will write something eventually, whether it’s documentation, or a project plan, or a requirements document.

The word processor might correct your spelling, but it won’t correct your lousy writing. The ability to communicate thoughts and ideas, in a clear, concise manner, is an absolutely invaluable skill that employers seek. The same goes for verbal communication. I used to work with a co-worker who doubled the length of every meeting he was in, because he could not answer a question in less than ten minutes. “Hey, Dennis, what time is it? ” “Well, that’s kind of interesting, because I just happened to be reading an article on cesium clocks and leap seconds and the history of the Gregorian Calendar and ... I’ll spare you the rest. XU-bp75mklu3ja@checkout. google. com © 2009 CAREERCUP 14 Interview War Stories You Can Count on Me, Just Not Until Early Afternoon Ahhh, 1999. The crest of the dot-com bubble, and the tightest labor market in history. Our company was racing to expand its development team, and we would have hired a German Shepherd if it knew HTML. Instead, we wound up hiring Ian. We should’ve hired the dog. Ian was a cheerful, friendly guy who had a gift of natural charisma. He got along fantastically with all of the interviewers, and seemed very intelligent.

Skillwise, he was adequate. He hadn’t written a single line of computer code outside of his college courses, and didn’t even have his own e-mail address. When we gave Ian the chance to ask us questions at the end of the interview, he asked about flexible work hours, and how soon he could take vacation time. Instead of showing an interest in the career opportunities, or in company’s growth prospects, he asked whether he could take the all-you-could-drink break room soda home with him. The questions grew more bizarre from there. Ian was very interested in our Legal Assistance benefit.

He wanted to know if it covered the cost of filing lawsuits, if it covered him if he got sued himself, if it applied to any lawsuits he currently was involved in, and if he could “theoretically” use it to sue the company itself. He also asked us if he could use it to help him “fix” some unpaid speeding tickets. In any other year, that should have been it for Ian right there. But, in 1999, we were hiring anybody who was even remotely competent. Ian collected paychecks from us for eighteen months, and he was about as productive as a traffic cone.

He usually sauntered into the office around ten-thirty with some sort of lame excuse (by my count, he had to wait for the cable guy sixteen times in a six-month period). He usually killed the morning by answering e-mail and playing ping-pong, before breaking for a two-hour lunch. After lunch, it was more pingpong, and maybe an hour of writing bad code, before bolting the office sometime around three. He was the dictionary definition of unreliable. Remember, your potential future team members need to know that they can rely on you. And they need to know that you won’t need constant supervision and hand-holding.

They need to know that you’re able to figure things out on your own. One of the most important messages that you, as a candidate, can convey in your interview is hiring me will make your lives easier. In fact, this is a large part of the reason for the famously difficult interview questions at places like Amazon and Google; if you can handle that kind of unpredictable pressure in an interview, then you stand a good chance of being useful to them on real projects. To cite a more subtle example, once I was on a four person team that was desperately trying to recruit new members to help work on an old pile of software.

It was a real mess; we’d inherited a nasty ball of spaghetti, and we needed people who could jump in, figure things out, and be part of the solution. There was one very smart fellow, Terry, who would have been a great asset for our team – 15 © 2009 CAREERCUP exclusively for XU-bp75mklu3ja@checkout. google. com Interview War Stories but we didn’t hire him, despite his excellent technical and personal skills. It was because he insisted on meticulous written instructions for every step of the coding process.

He wasn’t going to make a suggestion or take any initiative – or blow his nose, for that matter – without a mile-long audit trail and a dozen signatures. While he insisted that he worked that way for reasons of quality (a defensible point), we got the impression that it had more to do with butt-covering, and we simply didn’t have the time for that kind of bureaucracy. Terry would have been an excellent fit in a government or aerospace IT department, something that required ISO 9000 procedures. But he would have never fit into our team; he would have been a burden, not an asset.

XU-bp75mklu3ja@checkout. google. com © 2009 CAREERCUP 16 Interview War Stories My Spider Senses are Tingling I can think of lots of interviews that just fell into the general category of weird and uncomfortable: » » » » » » The Java coder who apparently considered hygiene optional, and had the interview room smelling like week-old blue cheese within ten minutes (my eyes were watering). The young fresh-out-of-college graduate with a tongue piercing that kept tick-tick-ticking against his teeth as he talked (after half an hour, it was like Chinese water torture).

The girl who wore an iPod through her interview, with the volume turned loud enough that she actually had to ask the interviewers to repeat themselves a few times. The poor, hyper-nervous fellow who was sweating like a marathon runner for half an hour. The girl who wore a T-shirt with an obscene political slogan to her interview. The guy who asked (seriously) at the end of his interview, “So, are there any hot chicks in our department? ” Those are the interviews where we politely thank the people for their time, shake their hand (except for the sweaty guy), then turn to each other after the door closes and ask – did that really just happen?

Nobody is saying that you have to be a bland, boring robot in a Brooks Brothers suit and tie. Remember, the interview team wants you to be “the one”, but they’re also very worried about the possibility that you’re going to be more of a distraction than an asset. Don’t talk or behave in a way that will set off their early warning radar. Whether or not somebody bothers to behave professionally during an interview is often a very good indicator of what kind of teammate they’re going to be. Rudimentary social skills are part of the answer to “Would I have a beer with this guy? , or at least, “Will I mind working next to this guy for six months? ” From the interviewer’s point of view, they’re picking a neighbor that they’re going to live and work with 200 hours per week for foreseeable future. Would you really want a neighbor that smelled like a hog rendering plant? 17 © 2009 CAREERCUP exclusively for XU-bp75mklu3ja@checkout. google. com Interview Questions Study hard, practice and good luck! How this Book is Organized The interview questions in this book are grouped into categories, with a page preceding each category offering advice and other information.

Within each category, the questions are sorted by approximate level of difficulty. Solutions for all questions are at the back. How to Use this Book An effective interview is not about memorizing interview questions, but rather, about applying an understanding of concepts and demonstrating your problem solving ability. Use these questions to find the gaps in your knowledge and to learn problem solving techniques that you can apply to new questions. Advice for Devs Your interview will be most likely not be conducted on a computer. Thus, when you practice the problems in this book, we recommend writing them down on paper first.

Then, type your solution into the computer exactly as you wrote it and see how you did. Special Advice for SDETs Not only do SDETs have to be great testers, but they also have to be great coders. Thus, we recommend that you complete the coding problems in this book with an eye for testing them. Even when the question doesn’t specifically ask it, you should ask yourself, “how would I test this? ” Remember: any problem can be an SDET problem. Suggestions and Corrections While we do our best to ensure that all the solutions are correct, mistakes will be made. Moreover, sometimes there is no “right” answer.

If you’d like to offer a suggestion or correction, please submit it at http:// xrl. us/ccbook XU-bp75mklu3ja@checkout. google. com © 2009 CAREERCUP 18 Applied Mathematics How to Approach: CHAPTER-1 Many of the so-called “Applied Mathematics” problems read as brain teasers at first, but can be worked through in a logical way. Just remember to rely on the rules of mathematics to develop an approach, and then to carefully translate that idea into code. Example: Given two numbers m and n, write a method to return the first number r that is divisible by both (e. g. , the least common multiple).

The Approach: What does it mean for r to be divisible by m and n? It means that all the primes in m must go into r, and all primes in n must be in r. What if m and n have primes in common? For example, if m is divisible by 3^5 and n is divisible by 3^7, what does this mean about r? It means r must be divisible by 3^7. The Rule: For each prime p such that p^a m (e. g. , m is divisible by p^a) and p^b n, r must be divisible by p^max(a, b) The Algorithm: Define q to be 1. for each prime number p less than m and n: find the largest a and b such that p^a m and p^b n let q = q * p^max(a, b) return q

Things to Watch Out For: 1. 2. Be careful with the difference in precision between floats vs. doubles. Don’t assume that a value (such as the slope of a line) is an int unless you’ve been told so. Prime Numbers 1. 2. Every number can be written as a product of primes. Example: 504 = 2^3 * 3^2 * 7 f x is divisible by y, then every prime factor in y must be found in x. Example: If 504 is divisible by y, then y could be 168 (2^3 * 3 * 7), or 21 (3 * 7), or 4 (2^2), or many other things. Y could not, however, be equal to 10 (5 * 2), since 5 is not found in x 19 © 2009 CAREERCUP exclusively for XU-bp75mklu3ja@checkout. oogle. com Applied Mathematics CHAPTER-1 1. 1 Write a method to generate the nth Fibonacci number _______________________________________________________________________pg 69 1. 2 Write a method to count the number of 2’s between 0 and n. EXAMPLE input: 35 output: 14 [list of 2’s: 2, 12, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 32] _______________________________________________________________________pg 70 1. 3 Given two lines on a Cartesian plane, determine whether the two lines would intersect. _______________________________________________________________________pg 74 1. Given two squares on a two dimensional plane, find a line that would cut these two squares in half. _______________________________________________________________________pg 75 1. 5 Write an algorithm which computes the number of trailing zeros in n factorial. EXAMPLE input: 11 output: 2 (11! = 39916800) _______________________________________________________________________pg 76 1. 6 Write a function that adds two numbers. You should not use + or any arithmetic operators. _______________________________________________________________________pg 77 1. Write a method to implement *, - , / operations. You should use only the + operator. _______________________________________________________________________pg 79 1. 8 Design an algorithm to find the kth number such that the only prime factors are 3, 5, and 7. _______________________________________________________________________pg 81 1. 9 A circus is designing a tower routine consisting of people standing atop one another’s shoulders. For practical and aesthetic reasons, each person must be both shorter and lighter than the person below him or her.

Given the heights and weights of each person in the circus, write a method to compute the largest possible number of people in such a tower. EXAMPLE: Input(ht, wt) : (65, 100) (70, 150) (56, 90) (75, 190) (60, 95) (68, 110) Output: The longest tower is length 6 and includes from top to bottom: (56,90) (60,95) (65,100) (68,110) (70,150) (75,190) _______________________________________________________________________pg 84 1. 10 Given a two dimensional graph with 6000 points on it, find a line which passes the most number of points. ______________________________________________________________________pg 86 © 2009 CAREERCUP 20 Arrays & Hash Tables How to Approach CHAPTER-2 While not all problem can be solved with a hash table, a shocking number of interview problems can be. Keeping track of which items you’ve already seen? Hash table. Needing a way to efficiently look up data? Hash table. The list goes on and on. You should become very extremely comfortable with hash tables: how to implement them and how to use them. Hash Tables A hash table is a data structure that associates keys with values for O(1) lookup.

Hash tables are frequently, though not always, implemented with an array. A simple implementation of a hash table that hashes a string to a Person is as follows: class HashTable { Person[] data = new Person[MAX_HASH_KEY]; int getId(string s) { /* return a key for this string */ }; bool contains(string key) { int id = getId(key); if (data247) return true; return false; } void insert(string s, Person p) { data[getId(s)]; } Note: This implementation does not handle collision. Collisions can be handled by “chaining” (eg, using a linked list), or a variety of other ways. Vector (Dynamically Resizing Array):

A vector, or a dynamically resizing array, is an array that resizes itself as needed while still providing O(1) access. A typical implementation is that when a vector is full, the array doubles in size. Each doubling takes a long time (O(n)), but happens so rarely that its asymptotic time is still O(1). 21 © 2009 CAREERCUP exclusively for XU-bp75mklu3ja@checkout. google. com Arrays CHAPTER-2 2. 1 Suppose we have an array a1, a2, ... , an, b1, b2, ... , bn. Implement an algorithm to change this array to a1, b1, a2, b2, ... , an, bn. _______________________________________________________________________pg 87 . 2 Design an algorithm and write code to remove the duplicate characters in a string without using any additional buffer. NOTE: One or two additional variables is fine. An extra copy of the array is not. FOLLOW UP Write the test cases for this method. _______________________________________________________________________pg 88 2. 3 You are given an array of integers (both positive and negative). Find the continuous sequence with the largest sum. Return the sum. EXAMPLE input: {2, -8, 3, -2, 4, -10} output: 5 [ eg, {3, -2, 4} ] _______________________________________________________________________pg 90 2. Design an algorithm to find all pairs of integers within an array which sum to a specified value. _______________________________________________________________________pg 91 2. 5 An array A[1... n] contains all the integers from 0 to n except for one number which is missing. In this problem, we cannot access an entire integer in A with a single operation. The elements of A are represented in binary, and the only operation we can use to access them is “fetch the jth bit of A[i]”, which takes constant time. Write code to find the missing integer. Can you do it in O(n) time? ______________________________________________________________________pg 93 © 2009 CAREERCUP 22 Bit Manipulation How to Approach: CHAPTER-3 Bit manipulation can be a scary thing to many candidate, but it doesn’t need to be! If you’re shaky on bit manipulation, we recommend doing a couple arithmetic-like problems to boost your skills. Compute the following by hand: 1010 - 0001 1010 > 1 1010 + 0110 1001^1001 0xFF - 1 1100^1010 1001 & 1100 0xAB + 0x11 If you’re still uncomfortable, examine very careful what happens when you do subtraction, addition, etc in base 10. Can you repeat that work in base 2? Things to Watch Out For: It’s really easy to make mistakes on these problem so, be careful! When you’re writing code, stop and thinking about what you’re writing every couple lines. When you’re done, check through your entire code. If you’re bit shifting, what happens when the digits get shifted off the end? Make sure to think about this case to ensure that you’re handling it correctly. 1 & 0 = 0 1 | 0 = 1 1 ^ 0 = 1 0 & 1 = 0 0 | 1 = 1 0 ^ 1 = 1 1 & 1 = 1 1 | 1 = 1 1 ^ 1 = 0 » And (&): 0 & 0 = 0 Or (|): 0 | 0 = 0 Xor (^): 0 ^ 0 = 0 Left Shift: x > 2 = 00000110 00011001 >> 4 = 00000001 exclusively for XU-bp75mklu3ja@checkout. oogle. com 23 © 2009 CAREERCUP Bit Manipulation CHAPTER-3 3. 1 Write a function int BitSwapReqd(int A, int B) to determine the number of bits required to convert integer A to integer B. EXAMPLE: _______________________________________________________________________pg 94 3. 2 If you were to write a program to swap odd and even bits in integer, what is the minimum number of instructions required? (eg, bit 0 and bit 1 are swapped, bit 2 and bit 3 are swapped, etc). EXAMPLE: _______________________________________________________________________pg 95 3. 3 Write a method which finds the maximum of two numbers.

You should not use if-else or any other comparison operator. EXAMPLE: _______________________________________________________________________pg 96 3. 4 Given a (decimal - e. g. 3. 72) number that is passed in as a string, print the binary representation. If the number can not be represented accurately in binary, print “ERROR” _______________________________________________________________________pg 97 3. 5 You are given two 32-bit numbers, N and M, and a two bit positions, i and j. Write a method to set all bits between i and j in N equal to M (eg, M becomes a substring of N located at i and starting j).

EXAMPLE: _______________________________________________________________________pg 99 3. 6 Write a function to swap a number in place without temporary variables. ______________________________________________________________________pg 100 3. 7 Given an integer, print the next smallest and next largest number that have the same number of 1 bits in their binary representation. ______________________________________________________________________pg 101 input: N = 10000000000, M = 10101, i = 2, j = 6 output: N = 10001010100 Input: 5, 10 Output: 10 Input: 10001010 Output: 01000101 Input: 31, 14 Output: 2 2009 CAREERCUP 24 Brain Teasers Do companies really ask brain teasers? CHAPTER-4 While many companies, including Google and Microsoft, have policies banning brain teasers, interviews still sometimes ask these tricky questions. Advice on Approaching Brain Teasers Don’t panic when you get a brain teaser. Interviewers want to see how you tackle a problem; they don’t expect you to immediately know the answer. Start talking, and show the interviewer how you approach a problem. In many cases, you will also find that the brain teasers have some connection back to fundamental laws or theories of computer science.

If you’re stuck, we recommend simplifying the problem. Solve it for a small number of items or a special case, and then see if you can generalize it. Example: You are trying to cook an egg for exactly 15 minutes, but instead of a timer, you are given two ropes which burn for exactly 1 hour each. The ropes, however, are of uneven densities - eg, half the rope length-wise might take only 2 minutes to burn. The approach: 1. 2. 3. 4. 5. 6. 7. What is important? Numbers usually have a meaning behind them. The fifteen minutes and two ropes were picked for a reason. Simplify!

You can easily time one hour (burn just one rope). Now, can you time 30 minutes? That’s half the time it takes to burn one rope. Can you burn the rope twice as fast? Yes! (Light the rope at both ends. ) You’ve now learned: (1) You can time 30 minutes. (2) You can burn a rope that takes X minutes in just X/2 minutes by lighting both ends. Work backwards: if you had a rope of burn-length 30 minutes, that would let you time 15 minutes. Can you remove 30 minutes of burn-time from a rope? You can remove 30 min of burn-time from Rope #2 by lighting Rope #1 at both ends and Rope #2 at one end.

Now that you have Rope #2 at burn-length 30 min, start cooking the egg and light rope #2 at the other end. When Rope #2 burns up, your egg is done! 25 © 2009 CAREERCUP exclusively for XU-bp75mklu3ja@checkout. google. com Brain Teasers CHAPTER-4 4. 1 Add arithmetic operators (plus, minus, times, divide) to make the following expression true: 3 1 3 6 = 8. You can use any parentheses you’d like. ______________________________________________________________________pg 103 4. 2 You have a 5 quart jug and 3 quart jug, and an unlimited supply of water (but no measuring cups). How would you come up with exactly four quarts of water?

NOTE: The jugs are oddly shaped, such that filling up exactly ‘half’ of the jug would be impossible. ______________________________________________________________________pg 104 4. 3 There is a building of 100 floors. If an egg drops from the Nth floor or above it will break. If it’s dropped from any floor below, it will not break. You’re given 2 eggs. Find N, while minimizing the number of drops for the worse case. ______________________________________________________________________pg 105 4. 4 A bunch of men are on an island. A genie comes down and gathers everyone together and places a magical hat on some people’s heads (e. . , at least one). The hat is magical: it can be seen by other people, but not by the wearer of the hat himself. To remove the hat, you must dunk yourself underwater at exactly midnight. If there are n people and c hats, how long does it take the men remove the crowns? The men cannot tell each other (in any way) that they have a hat. FOLLOW UP Prove that your solution is correct. ______________________________________________________________________pg 106 4. 5 There are 100 closed lockers in a hallway. A man begins by opening all the 100 lockers. Next, he closes every second locker.

Then he goes to every third locker and closes it if it is open or opens it if it is closed (eg, he toggles every third locker). After his 100th pass in the hallway, in which he toggles only locker number 100, how many lockers are open? ______________________________________________________________________pg 108 © 2009 CAREERCUP 26 C / C++ How To Approach: CHAPTER-5 A good interviewer won’t demand that you code in a language you don’t profess to know. Hopefully, if you’re asked to code in C++, it’s listed on your resume. If you don’t remember all the APIs, don’t worry—your interviewer probably doesn’t either!

We do recommend, however, studying up on basic C++ syntax. Pointer Syntax int p = v = Foo int *p; // Defines pointer. &q; // Sets p to address of q. *p; // Set v to value of q. *f = new Foo(); // Initializes f. k = f->x; // Sets k equal to the value of f’s member variable. C++ Class Syntax class MyClass { private: double var; public: MyClass(double v) {var = v; } ~MyClass() {}; double Update(double v); }; double Complex::Update(double v) { var = v; return v; } C++ vs Java: A very common answer in an interview is “describe the differences between C++ and Java. If you aren’t comfortable with any of these concepts, we recommend reading up on them. 1. 2. 3. 4. 5. 6. Java runs in a virtual machine. C++ natively supports unsigned arithmetic. In Java, parameters are always passed by value (or with objects, their references are passed by value). In C++, parameters can be passed by value, pointer, or by reference. Java has built-in garbage collection. C++ allows operator overloading. C++ allows multiple inheritance of classes. Thought: Which of these might be considered strengths or weaknesses of C++ or Java? Why? In what cases might you choose one language over the other? 7 © 2009 CAREERCUP exclusively for XU-bp75mklu3ja@checkout. google. com C / C++ CHAPTER-5 5. 1 What is the difference between a struct and a class? Where would you use each? ______________________________________________________________________pg 109 5. 2 Write a method to print the last ten lines of an input file using C. ______________________________________________________________________pg 110 5. 3 Compare and contrast a hash table vs. an STL map. How is a hash table implemented? If the number of inputs are small, what data structure options can be used instead of a hash table? _____________________________________________________________________pg 111 5. 4 How do a virtual functions work in C++? ______________________________________________________________________pg 112 5. 5 What is the difference between deep copy and shallow copy? Explain how you would use each. ______________________________________________________________________pg 113 5. 6 In a class, the ‘new’ operator is used for allocating memory for new objects. Can this be done using malloc? If yes, how? If no, why not? Are there any restrictions associated with the use of malloc in place of new? _____________________________________________________________________pg 114 5. 7 What is the significance of the keyword “volatile” in C? ______________________________________________________________________pg 115 5. 8 What is name hiding in C++? ______________________________________________________________________pg 116 5. 9 Why does a destructor in base class need to be declared virtual? ______________________________________________________________________pg 117 5. 10 Write a method that takes a pointer to a Node structure as a parameter and returns a complete copy of the passed-in data structure.

The Node structure contains two pointers to other Node structures. For example, the method signature could look like so: Node* Copy(Node* root); Note: Do not make any assumptions about the data structure – it could be a tree, linked list, graph etc. Feel free to choose the language you are most comfortable with (C# or C++ are preferred) In addition to the function code, write a complete suite of unit tests for this problem. ______________________________________________________________________pg 119 5. 11 Write a smart pointer (smart_ptr) class. _____________________________________________________________________pg 120 © 2009 CAREERCUP 28 Counting and Combinatorics How to Approach: CHAPTER-6 While some problems in this chapter are simply coding problems, understanding the mathematical solution will help you “sanity check” your solution. For example, if you know how many subsets there are of a set, you can check to make sure that your algorithm to print all subsets will give you the correct number of subsets. When computing the number of ways of doing something, think about doing it step by step. The following two examples will illustrate this technique.

How many ways can you pick k elements from n elements, if order matters and elements are not replaced? Eg - if we pick 5 different letters, “abcde” is considered to be different from “edcba”. The Approach: We have n choices for the first draw. For the second draw, we only have n-1 since one is removed. Then n-2, …. When we draw k times, we get down to n-k+1 choices on the last draw. So, n * (n-1) * (n-2)*… * (n-k+1) The Solution: n! / (n-k)! How many ways can you pick k elements from n elements, if order does not matter and elements are not replaced? We’re now just throwing letters into a bucket. Picking “a, b” is the same thing as “b, a”.

The Approach: If you compare this problem to the previous one, we’ve essentially double (or triple, quadruple, etc) counted items. That is, “abc”, “acb”, “bac”, “bca”, “cab”, “cba” were all considered unique in the previous solution but now they’re considered the same. Just how many times has “abc” been included (in its other forms)? 3! times, since there are 3! ways of rearranging “abc”. In fact, every item has been included 3! times, when it should have been included just once! So, we divide our previous answer by 3! (or, more generally, k! ). We now get n! / (k! * (n-k)! ). This solution is often written as n-choose-k or nCk. 9 © 2009 CAREERCUP exclusively for XU-bp75mklu3ja@checkout. google. com Counting and Combinatorics CHAPTER-6 6. 1 In how many different ways can a cube be painted by using three different colors of paint? ______________________________________________________________________pg 121 6. 2 Imagine a robot sitting on the upper left hand corner of an NxN grid. The robot can only move in two directions: right and down. How many possible paths are there for the robot? FOLLOW-UP Imagine certain squares are “off limits”, such that the robot can not step on them. Design an algorithm to print all possible paths for the robot. _____________________________________________________________________pg 122 6. 3 Write a method to compute all permutations of a string. ______________________________________________________________________pg 123 6. 4 Implement an algorithm to print all valid (eg, properly opened and closed) combinations of n-pairs of parentheses. EXAMPLE: input: 3 (eg, 3 pairs of parentheses) output: ()()(), ()(()), (())(), ((())) ______________________________________________________________________pg 124 6. 5 Write a method that returns all subsets of a set. ______________________________________________________________________pg 125 2009 CAREERCUP 30 Database How to Approach: CHAPTER-7 You could be asked about databases in a variety of ways: write a SQL query, design a database to hold certain data, or to design a large database. We’ll go through the latter two types here. Small Database Design Imagine you are asked to design a system to represent a school’s registrar: course information, departments, course enrollment, teachers, etc. What are the key objects? Student. Professor. Course. Department. How do they relate to each other? *NOTE: I’m going to make some assumptions here for the purposes of writing up this explanation.

In your interview, don’t make assumptions! Ask your interviewer instead. Many-to-Many: » A course can belong to multiple departments, and each department can have multiple courses. So, create a separate table DepartmentCourse that acts as a “pairing” of the two. DepartmentCourse has just a department_id field and a course_id field. A student can be in multiple courses, a course can have multiple students. So, do the same as above and create a StudentCourse table. A course only has one professor. A professor can teach multiple courses. So, add a field professor_id to the Courses table. » One-to-Many: »

Large Database Design When designing a large, scalable database, joins (which are required in the above examples), are generally very slow. Thus, you must denormalize your data. Think carefully about what when data will be used—you’ll probably need to duplicate it in multiple tables. 31 © 2009 CAREERCUP exclusively for XU-bp75mklu3ja@checkout. google. com Database CHAPTER-7 7. 1 Write a method to find the number of employees in each department when we have the following tables: ______________________________________________________________________pg 126 7. 2 What are the different types of joins?

Please explain how they differ and why certain types are better in certain situations. ______________________________________________________________________pg 127 7. 3 What is normalization? Explain the pros and cons. ______________________________________________________________________pg 128 7. 4 Draw a entity-relationship diagram for a database with companies, people, and professionals (people who work for companies). ______________________________________________________________________pg 129 7. 5 You have to design a database that can store terabytes of data. It should support efficient range queries. How would you do it? _____________________________________________________________________pg 130 Employees containing: Emp_ID, Emp_Name and Dept_ID (Primary key) Departments containing: Dept_Name and Dept_ID (foreign key) © 2009 CAREERCUP 32 Debugging Existing Code How to Approach CHAPTER-8 Sometimes, in an interview, an interviewer asks you to look at a piece of code and identify the mistakes. We recommend the following approach: 1. 2. 3. Examine the code and understand what it’s expected to do. Ask your interviewer what types of data it’s expected to handle, where it’ll be used, etc. Look for syntax errors: does everything type check? s the class declaration correct? Look for “hot spots”: » » » » » 4. » » 5. If you see float and doubles, check for precision errors If you see division, check for rounding errors If you see memory allocation, check for memory leaks If you see unsigned ints, check to see if the int might ever be negative If you see bit manipulation, check for correctness The “normal” case The boundary cases (null, 0, 1, MAX, etc) Run through the code with a few examples: Does it do everything it’s expect to? For example, if the code is supposed to return everyone in a database under 21, does it only look for students?

Maybe it should be looking for teach-ers as well? Does it handle unexpected cases? What if it takes in a list and it has a loop? 6. Further Advice 1. 2. Look at the space and time complexity—can you improve it? Correct the mistakes in the code. But do so carefully! Don’t simply make changes until it works. Deeply understand the issues and then correct them. 33 © 2009 CAREERCUP exclusively for XU-bp75mklu3ja@checkout. google. com Debugging Existing Code 8. 1 Explain what the following code does: ((n & (n-1)) == 0) CHAPTER-8 ______________________________________________________________________pg 131 8. Find the mistake(s) in the following code: unsigned int i; for (i = 100; i ::Other { int foo() { printf(“here we are ”); }; }; main() { typedef Foo typedef Derived Derived_inst; Derived_inst ii; ii. foo(); } ______________________________________________________________________pg 133 © 2009 CAREERCUP 34 Games How To Approach: CHAPTER-9 Sometimes interviewers ask these problems simply because they’re “fun,” but often, it’s also because “game” problems are heavy on object oriented design. Gaming problems tend to be more “free form” and thus they give you the chance to demonstrate how you really code.

Define Data Structures When implementing something so free form, ask yourself, “Where can I define a class or a struct? ” When in doubt, define a new class or struct. It tells the interviewer that you care about the maintainability of your code. Validate Your Assumptions Be careful about making assumptions. Suppose you’re asked to implement the word game Scrabble. Don’t assume that the dictionary will be in English—or even in that character set. It could be in any language! Ask your interviewer lots and lots of questions so that you know what to implement. Are you solving this problem once, or many times?

Sometimes the solution will change depending on whether or not your code will be called multiple times. For example, suppose you’re asked to find all anagrams of a word. If you’re calling this code just once, it may be fastest just to rearrange the letters and check if they’re in the dictionary. But, if you’re going to call the code multiple times, it’s now fastest to precompute data by iterating through all the words in the dictionary. Can you generalize your code, or part of it? If you really want to go above and beyond, try writing your code as though it were a more generalized case.

For example, if you’re trying to figure out if a tic-tac-toe board has a winner, you might suggest to your interviewer solving it for the more general NxN case. If you go down this path though, be warned—sometimes problems are trickier than they appear. Also, make sure you discuss this with your interviewer so he/she knows what you’re doing. 35 © 2009 CAREERCUP exclusively for XU-bp75mklu3ja@checkout. google. com Games CHAPTER-9 9. 1 Design an algorithm to figure out if someone has won in a game of tic-tac-toe. ______________________________________________________________________pg 135 9. The Game of Master Mind is played as follows: - The computer has four slots containing balls that are red (R), yellow (Y), green (G) or blue (B). For example, the computer might have RGGB (eg, Slot #1 is red, Slots #2 and #3 are green, #4 is blue). - You, the user, are trying to guess the solution. You might, for example, guess YRGB. - When you guess right color for the right slot, you get a “hit”. If you guess a color that exists but is in the wrong slot, you get a “psuedo-hit”. For example, the guess YRGB has 2 hits and one pseudo-hit. For each guess, you are told the number of hits and pseudo hits.

Write a method that, given a guess and a solution, returns the number of hits and pseudo hits. ______________________________________________________________________pg 137 9. 3 There is an 8x8 chess board in which two diagonally opposite corners have been cut off. You are given 31 dominos in which a single domino can cover exactly two squares. Can you use the 31 dominos to cover the entire board? Prove your answer (by providing an example, or showing why it’s impossible). ______________________________________________________________________pg 138 9. Find a way to arrange 8 queens on a chess board so that none of them share the same row, column or diagonal. ______________________________________________________________________pg 139 9. 5 Othello is played as follows: Each Othello piece is white on one side and black on the other. On your turn, you place a piece on the board so that your color is facing up. You must pick a spot such that your opponent’s pieces are either on the left and the right, or on the top and the bottom. All of your opponent’s pieces on the line between two of yours are then turned over, to become yours. Your goal is to own the most pieces.

Design the game Othello. Write a method to check whether someone has won the game. ______________________________________________________________________pg 141 © 2009 CAREERCUP 36 Java How to Approach: CHAPTER-10 While Java related questions are found throughout this book, this chapter deals with questions about the language and syntax. You generally will not find many questions like this at the larger software companies (Microsoft, Google, Amazon, etc), which tend to avoid ‘trivia’ based questions, but these questions are very common at many smaller companies. What do you do when you don’t know the answer?

If you don’t know the answer to a question about the Java language, try to figure it out by doing the following: (1) Think about what other languages do. (2) Create an example of the scenario. (3) Ask yourself how you would handle the scenario if you were designing the language. Your interviewer will likely be equally—or more—impressed if you