# Brain teaser Interview Questions

interview questions shared by candidates

## Brain teaser Interview Questions

### Project Director at UnitedHealth Group was asked...

How do you feel about PMI-MN? 4 AnswersThis questions was far too open ended and non-specific. By PMI-MN, I take it you are referring to the Project Management Institute of Minnesota - I whole heartedly support the organization and the ability to assimilate new methods and knowledge networking through this and similar bodies. PMI as an organization is useful and membership demonstrates a commitment to staying up with industry best practice; however, I will openly state that the PMP itself has become an irritant and created a false hiring environment. Most contractors seem to feel every project must have a PM assigned who has a PMP. Most employers seem to feel that this is a necessary requirement. Between this and the availability of PMP training at most community colleges, we are now faced with a burgeoning population of largely unskilled "Project Managers" who are not worth their weight in weekly reports. They generally fail to understand true project ownership, are perfectly willing to allow projects to fail so long as they can point the finger, and add little more than an over-inflated rate to my billings. Companies need to find more rigorous qualifications and interview techniques and stop relying on the PMP as a qualifer. By relying primarilly on the PMP as a qualifier, as employers, we are participating in cost inflation that does not bring value to our objectives. Show More Responses I've the same exp in UHG |

### Web Technology Intern at Riot Games was asked...

“Imagine that you have three boxes, one containing two black marbles, one containing two white marbles, and the third, one black marble and one white marble. The boxes were labeled for their contents - BB, WW, BW - but someone has switched the labels so that every box is now incorrectly labeled. You are allowed to take one marble at a time out of any box, without looking inside, and by this process of sampling you are to determine the contents of all three boxes. What is the smallest number of drawings needed to do this?” 4 Answers1 Four. If you draw a white bead, then draw out of another box. If you draw a white bead from box 2, then draw from either box 1 or box 2 to discern the identity of all 3. If you draw a black bead on your second draw (box 2), then you will need at most two more draws to discern the identity of all three. Knowing the color of one bead from all three boxes doesn't allow us to label all 3 correctly, so in the scenario where we draw a white bead from box 1 and a black bead from box 2, picking from box 3 doesn't do us any good. To solve this problem, we need to find BW in a box and any other bead, or we need to know the location of all three beads of a single color The answer is 3. People would normally think 4 because of 2 reasons the average person would want to identify atleast 1 marble in all 3 boxes before pulling another which would force atleast 1 more draw equaling 4 before they may solve the problem. The other reason people would say 4 is because they overlook the chances of being lucky and drawing a black and white from the same box. If you look at it using math. one instantly thinks they have a 1/3rd chance of getting the black and white marble within 3 tries so they naturally dont think of that possibility. Truth be told if one is lucky enough it only takes 3 if you pull 1 marble from 2 boxes and they are the same color your chance of solving the puzzle is 100% on the 3rd draw. if you pull the same color the other box has the duel color if you choose opposite colors than the other box has the same color. Remmember the question does not say you must draw from boxes in order or in rounds. the question also does not state its looking for the smallest number of draws with a guarantee correct answer its just asking for the smallest amount possible. Show More Responses The key thing here is that the box does not contain what it says on the label. As such you can guarantee the contents of each box with one draw. Here's how: Draw a marble from the box labeled BW (since it is labeled BW it must be either BB or WW) If you draw a white for example you know 100% that it is the WW box. Then there are only two boxes left labeled WW and BB in this example and the only two things that they can be are BB or BW. The box labeled BB cannot be BB and so hence must be the BW. This leaves the box labeled WW to be BB by elimination. Same thing works if you pick a black marble first. The key is picking from the BW box in the start and confirming what it actually is. One draw is the smallest number needed. |

### Specialist at Apple was asked...

What is your main weakness? 4 AnswersAnswer however you like, just be prepared. I wouldn't say I have a weakness but If make a mistake it's my job to learn from it and get better at it. first of all we discover our weakness,when we fail to do/achieve something perfectly.but once we discover it,and we learn to overcome it,it becomes one of our power/ability,so you would better ask what are you'r powers?and they will be achieved during our life course througjh experience Show More Responses The point about this question is to test self-awareness. The answer is not to say "I work too hard" or "too detail oriented" or some other non-weakness answer. The correct answer is to ask yourself what skill does this job not require, and then you pick a weakness from that set of skills for which you give something constructive. Eg. An engineer position does not need public speaking skills. Say you get nervous when speaking to large audiences and you mitigate that by preparing well.. |

The most difficult question asked was had I ever made a non productive stop, for every LP this is a difficult thing to talk about. 3 AnswersAnswered the question and explained what I did wrong and what I learned from it. I'd have simply said something like, "Yes, but only for a bathroom break". Or, if you don't suck at your job, your answer would be "No". |

Given an array of integers, all but one of which appears an even number of times, find the one integer which appears an odd number of times. Upon completion, asked to improve the algorithm in terms of both time and space, eventually asked to do it in O(n) time and constant space. 4 Answersxor the entire array, all the integers which appear an even number of times will cancel eachother out int[] theArray = new int[]{1, 1, 2, 2, 3, 3, 3, 4, 4, 10, 10, 10, 10, 10, 11, 11, 12, 12}; Map theMap = new HashMap(); for (int i = 0; i mapKeys = theMap.keySet(); for(int keyInt : mapKeys) { if(theMap.get(keyInt) % 2 != 0) { System.out.println(keyInt + " occurs odd number of times"); } } } I was also asked this in 2010,march. Show More Responses XOR |

Question from director: "... four people need to cross a bridge at night, there is only one flash light and only one person can walk on the bridge at a time. How do would you get them all across the bridge?" 7 AnswersThe first person carries the second person across on his back. The second person goes back to retrieve the third person and carries him across. The third person goes back for the fourth person and carries him across. Nope, only 1 person at a time, remember? just have the last person shine the flashlight on the bridge while the other people cross and then cross last. Solution 1: Question said cross the bridge and did not say need to stay on the other side of the bridge. Person 1 to 3 cross with flashlight. Then any one of them return with flash light for the 4th to cross with flash light. One person would remain but all would have crossed. Solution 2: Whoever got to the other side go buy 3 more torch lights so all 4 can cross with minimal back and forth. Solution 3: Tie a really long string to the flash light. After first person uses it to get across, second person pulls it back by the string. Repeat the process. Show More Responses This is a UX question; each person must experience the Journey with the flashlight. In a situation that there isn't a string, each person takes the flashlight up and down the bridge, while marking or taking metal note of the path they take, while going back. The person will then return the flash light to another while walking back without the flashlight. Once the person gets back to the others, he/she drop the flashlight and cross the bridge following the pattern or marking that he or she created. The pattern and design will be followed by everyone. Leaving the flashlight for another person to use. It is about creating a design that others can use and be successful at. Well, why do you need a flashlight to cross a bridge? A blind person can cross a bridge, no? Can you not keep a hand on the railing and feel your way across? Can you not feel the rumble of traffic passing and keep away? Sure, it feels safer with a light, so let's go with that. You need to see what's ahead, so the first three people take turns shining the light from behind as one person crosses at a time. Then the fourth person crosses with the flashlight. The first person walks across, turns around, and shines the light back at the rest of the group. Then the group has a light to walk toward. If a UX director asks this question, he wants to see how much of real UX designer you are, and how methodical you approach this task. A good UX designer needs to understand the real problem first. Based on the information given we can only make broad assumptions. A hypothesis based on limited data is a good starting point, but before we jump to premature "solutions", the first task is to do more digging. We need to ask questions (and do research) to understand the actual problem before we can propose a a fitting solution - a user experience that truly solves the unique problem these four people have in their specific situation (it might even turn out that they don't need to cross a bridge at night but need something completely else, but let's not go that far here). So - based on the information given, we don't know what type of bridge it is (does it have a railing, is the bridge lit, short, long, is there even pavement or gravel and potholes, is there traffic, etc...), we need to understand WHY only one person can walk on the bridge and whether the people even need to walk (they might be able to drive, maybe there is a bus that can transport them). Where is the flash light, what type of flash light is it And who are these individuals? What is the relationship between these people? Do they all have the same motivation to cross the bridge? WHY do they need to cross the bridge? Is that really what they need, or do they have a different problem? Also, are they all on the same side? Why do they need to cross the bridge at night, do they have to cross the bridge every night or just once? Etc. etc. -You get the point. In addition: What are my resources to get them over the bridge? Which technical and business opportunities and constraints do I have? In which time duration do I have to get them cross the bridge? Fun exercise for a UX candidate. |

### Software Engineer at Cisco Systems was asked...

If you have a square room with no roof, and you had four flagpoles you had to plant on the walls so that each flagpole touched two walls, how would you do it? 3 Answerspaint one half of the flag pole on one wall and the other half on the other wall, so that you are touching two walls. Not sure if this would be allowed, but I thought put each flagpole horizontal instead of vertical. Then they are fixated to the wall and touch two sides (assuming the flagpoles are long enough). The answer was that by planting them on the corners, each one is touching two walls because each corner is part of two walls. I wanted to pierce two walls with a pole horizontally too. They said it was an innovative solution. |

### Service Engineering Intern at Cummins was asked...

You are in a boat which is in the middle of a pond and you are holding a rock in your hand. You throw the rock into the lake. Does the water level of the lake rise? 6 AnswersNo right or wrong answer. They just want to see how you think. The water level will drop. When you hold the rock, the extra displaced volume of water equals the weight of the rock. When you throw the rock into the lake, displaced volume is the size of the rock, which is less. both wrong. the water level does not change. at first the density the boat has is density of the boat + density of rock affecting water level. in the final situation the boat has gotten rid of the rock's density, but the rock (and its density) have been added to the lake, so we still have density of boat + density of rock affecting water level. location doesn't change physics. Show More Responses The water level decreases when the rock leaves your hand, then increases again when the rock enters the water. Does the final answer depend on the rock's density compared to the density of water? While the rock is in the boat the displaced water has the same weight as the rock when the rock is in the water the volume of water displaced is the same as the volume of the rock. So the level of the water rises or falls depending on the density of the rock |

### Software Engineer II at Blackbaud was asked...

You have 2 jars and 50 black beads and 50 white beads. How many would you put of each color in each jar so that if a bead was randomly selected from both jars, you had the greatest chance they would match? You have to put all of the beads in the jars. 5 Answers1 of either color in the first jar (100% chance to get that color), the rest in the 2nd jar (very close to a 50% chance to get a matching color). If you fill each jar with half black and half white then you will have a 50/50 chance of drawing a match. If you put any more than half of a color in jar number 1, then you will increase your odds of drawing that color from jar 1, but since there will be a smaller number of those beads in jar 2, you will decrease the odds of drawing that color from jar 2. Therefore any configuration other than half of each color in each jar will result in less than 50/50 odds of drawing a match (like in the answer above). As long as the ratio of black beads to white beads is 1:1 in both jars, it doesn't matter. Show More Responses One of each jar This question is too easy |

### Intern at J H Darbie &Co was asked...

How far away is Russia from the US? 3 Answers100 miles It depends on whether you want to measure it by distance between the two countries literally, their military presence, economically etc. Not too far at all. Yah...they asked me how to cut 6 pcs of cake into 8 pcs? |