Top 20 Puzzles for Interviews

Companies now use various talents, and skill gauging techniques and interview puzzles are one of them. These brain-teasing scenarios allow recruiters and hiring teams to test your lateral thinking and problem-solving skills. 

These questions are part of a job interview for candidates applying for positions requiring a lot of critical thinking, such as analysts, coding, and programming. However, when you prepare for an interview these days, you may want to practice solving and answer some mind-twisting and head-scratching puzzles and hypothetical scenarios. 

In this post, you are going to learn about the 20 best puzzles for interviews asked by some of the most successful companies in the world. However, to add a bit of challenge, you will have to explore the answer by yourself. This exercise will help you hone your critical thinking and reasoning skills for that next dream job interview. 

So without further ado, let us dive right in and look at what interview puzzles are and the top 20 puzzles to give you an idea about the variations. 


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Explanation of Interview Puzzles

An interview puzzle is a critical thinking scenario, just like brain teasers. These problems require you as an interviewee to rely on your problem-solving and lateral thinking capabilities. The primary purpose why interviewers use interview puzzles is to find out if you are a good fit for their company. 

However, not all job interviews come with an interview puzzle. For example, if you are applying for a receptionist position or as an administrative assistant, you most likely do not have to worry about having to solve an interview puzzle. It is because your job may not require any high-level thinking and analysis. 

The job interview puzzles are primarily for people applying for either critical job roles or as specialists in a particular field such as Information Technology. 

You must remember that it is not always necessary to answer or solve the interview puzzles correctly. Sometimes, the only purpose of presenting you with these head-scratchers is that the interviewer wants to see your mindset and approach to solving a problem. 

However, it would help if you can practice some of the puzzles prior to attending an interview. This will increase your chances to answer them correctly. Moreover, these practice sessions will also improve your reasoning skills and help you prove your competency and ability to deal with real-life problems in an efficient manner. 

How to Approach Puzzle Interview

In order for you to try and solve puzzles for interviews, here are five basic steps that you must remember. 

  1. Use Your Critical Thinking

The first step for you is to think about the puzzle in front of you. It would be best for you to determine the nature of the puzzle, i.e. if the interviewer wishes you to solve a riddle or a numerical answer to the problem they want you to find. 

Once you know the expected outcome of the puzzle, you can apply problem-solving skills to get to the right solution. 

  1. Understand the Objective

Once you get to know the nature of the puzzle and what outcome you must achieve, the next step is to ensure that you understand the scenario and requirements clearly. Do not be shy to ask for further clarifications from the interviewers. 

Some interview puzzles are more complicated in nature, and asking for clarification may help you understand the presented problem better. Asking questions about the puzzle will also show the recruiters that you know when to ask questions and are eager to seek resources and information to complete the given task. 

Apart from your credentials and other talents, the interviewers may appreciate your self-initiative and eagerness to learn everything about the problem. 

  1. Using Your Knowledge

It is always wise to fall back to your basic problem-solving skills. Although these puzzles seem like brain-teasing behemoths, most of them require common mathematical approaches to reach a definitive solution. 

You can work on them by combining both information and lateral thinking to make sense out of these problems. 

  1. Do not be Shy to Show-off Your Skills

As you work on the interview puzzle in front of you, it would be a good idea to let the interviewers see how you process and reason. You can explain why you are solving the puzzle in a certain way. This way, the interviewers will be able to learn about your planning skills, execution strategies, and the variety of solutions you come up with under pressure. 

Interview puzzles are an excellent opportunity to showcase your analytical skills, prior knowledge, and critical thinking mind. Explanation of how you arrived at a solution for the puzzle will be a perfect means to demonstrate your skills. 

  1. Offer a Solution

Whatever you do, always be sure to come up with a solution, even when it is not the right one. Giving an answer will show that you used some logic, reasoning, and critical thinking to come up with a specific solution. 

Sometimes, it is more important for an employer to see that you tried to offer a solution than giving up. In most cases, you must offer a solution for every scenario presented to you during an interview. 

20 Best Interview Puzzles

In this section of the article, we have gathered the top 20 puzzles for interviews by some of the biggest companies such as Amazon, Adobe, Bloomberg, Facebook, Microsoft, etc. So let us get started. 

  1. 100 People in a Circle

This puzzle is a medium difficulty level algorithmic brain-teaser. There are 100 people standing around in a circle in order of 1 to 100. Person no. 1 has a sword, and he kills the person next to him, i.e., no.2, and gives the sword to the person next to no.2 that will be no.3. 

Now all the people do the same until there is a single survivor. Now your task is to determine which number is the last survivor. 

  1. Ants-on-a-Triangle

Imagine there are three ants sitting on a triangle at each corner. Now each ant picks a random direction and starts to move along the triangle’s edge. The probability of none of these ants are going to collide with one another is 1/K. 

You have to find out the value of “K.”

  1. A Fake amongst 12 Coins

This interview puzzle is an algorithmic brain-twister with medium difficulty levels asked frequently by Bloomberg and Microsoft. Let us see if you can unlock the solution. 

You have 12 identical-looking coins in front of you; however, one of them is a counterfeit. The counterfeit coin happens to be lighter than the rest of the 11 genuine coins. The puzzle wants you to determine the minimum number of weighings in order for you to identify the counterfeit coin. For weighing, you get a two-pan balance scale without any weights. 

Remember, the answer must be an integer and does not require you to mention any decimal places. 

  1. Crossing the Bridge

This is an algorithmic puzzle with a medium difficulty level. This puzzle frequently appears in interviews in Google and Microsoft. 

The puzzle is four people require crossing a wobbly bridge during nighttime. Unfortunately, they only have a single torch; however, it is too dangerous to cross the bridge without one. The bridge is also strong enough that it can support only two people at one time. 

Not all four people take the same amount of time to cross the bridge. Time required crossing the bridge for each person, i.e., 1 min, 2 minutes, 7 minutes, and 10 minutes. 

When two people try to cross this bridge together while sharing the flashlight, they walk at the pace of the slowest person. So, determine the minimum time required for all people to cross the bridge? 

You must provide an answer in a number of minutes. The answer will be an integer. 

  1. 2 Eggs & 100 Floor

This is one of the topmost interview puzzles with a hard difficulty level. You will require honing all your lateral thinking, knowledge, and problem-solving skills to solve this one. 

There is a tall 100-floor building. If you drop an egg from the Nth floor or higher, it will break. If you drop the egg from any floor below the Nth floor, it will not crack. Now you have two eggs only to find the “N,” and you must minimize the number of drops when it comes to worst-case scenarios. 

You must remember these are strong eggs, and you can drop them multiple times without cracking them. However, remember that they will not break as long as you drop them from floors below the “threshold” or “Nth” floor. 

If you drop the egg from above the Nth floor, it is going to break. Your job task is to find the minimum amount of drops you will require to find the Nth floor. The answer will be an integer without any decimal values.  

  1. Chessboard Reassembly

Another challenging interview puzzles that the mind helps you develop your critical thinking and mathematical skills to get the dream job. 

There is a square in front of you with 8x8 chessboards. These blocks are mistakenly colored into blocks of two different colors. You must cut this board along certain lines while separating its column and rows so that you can reassemble the 8x8 chessboard is re-arranging the pieces. 

https://s3.ap-south-1.amazonaws.com/afteracademy-server-uploads/chessboard-reasembly.png

Your task is to find out the minimum number of chessboard pieces that the entire board needs cutting in. You can see the chessboard in the picture below

  1. Fake Note

This is an easy one but a true brain-teaser. Try using your skills to solve this one without any help. 

A Man (X) buys a product that is worth $50 from a local shopkeeper (Y). He pays the shopkeeper using $100. Realizing that he does not have the change, (Y) the shopkeeper changes $100 with another shopkeeper (Z) and pays the remaining $50 to the man (X). 

After a couple of days, Z realizes that the note turns out to be a fake. He tells this to Y and collects his $100 back from him. So, how much money did (Y) lose in this entire process? 

  1. Finding a Celebrity

Another one of the difficult interview puzzles from the algorithmic domain. Companies like Microsoft, Facebook, and Yahoo use this to gauge the skills and abilities of potential job candidates. 

Imagine you are attending a party with an “N” number of people. Now amongst these people, there may also be a celebrity in attendance. The definition of this celebrity is that all of the other (N-1) attendees know him or her. However, the celebrity does not know any of those people. 

Your task is to find out who this celebrity is or even verify that there is no celebrity amongst the attendees. The only thing this puzzle allows you to do is asking a question such as “Hi “A,” do you know “B”? The whole idea behind this exercise is to get the information whether A knows B and so on. 

You must find out who the celebrity is and whether there is even one or not by asking as fewer questions as you possibly can. You can assume that all the guests at this party are very polite and approachable (even the celebrity), and they will answer any question you ask correctly. 

So what will be the maximum questions your algorithm requires in order for you to solve this puzzle? 

Option 1: N-1

Option 2: N log N

Option 3: 3N-3

Option 4: 2N-2

  1. Find Daughters’ Ages

Fancy attempting this brain-teaser? Well, let us see how well you do. 

Two MIT math graduates run into each other at a Fairway located near the upper west-side. They have not met each other in 20 years. 

The first graduate says to the other: “How have you been?”

The second one replies: “Great! I am married and have three daughters.”

First one: “really! How old are your daughters?”

Second grade: “well, the total product of my daughters’ ages is 72. The sum of their collective ages is exactly the same as the number you can see on a building over there.” 

First one: “Right, ok, but wait, I still do not know.”

Second: “Oh, I am sorry, my oldest daughter just learned to play the piano.” 

First: “That is wonderful! My oldest girl is the same age too.”

So, your question is: how old are their daughters.

You must respond with their daughter’s age in ascending order as well as concatenated together. There are no spaces allowed. 

  1. Monkeys and Doors

This is going to take some serious brainstorming. 

If you ever fancy applying for companies such as Amazon, Adobe, Google, or Microsoft, always go in after solving this one. Who knows, you might get lucky to get the same or similar puzzle during the job interview. 

You have 100 doors, and all of them are closed. In a cage nearby, there are 100 monkeys. Now the first monkey comes out of the cage and runs along the doors opening each of them. Then the other monkey comes out of the cage and running with the open doors while closing 2nd, 4th, 6th, and all doors with even numbers. 

The third monkey comes out and only attends the 3rd, 6th, 9th, and every third door while closing the opened door and opening the closed door. After all of the 100 monkeys have done their work in a similar fashion, how many doors will be open in the end? 

  1. Round Table – Coin Game

Imagine two players are playing a game on a circular table with an unspecified diameter. Each of these players has access to an infinite supply of coins. They take turns placing a single coin on this table in such a way that the coins do not overlap each other. You can assume that the diameter of this table is way larger than the diameter of the coins used. 

A player will be a winner if he or she makes the last legal move. So, find out which of these players (If any) has got a strategy to guarantee a win? 

Option 1: Player 1

Option2: Player 2

Option3:  Neither of the players

Option 4:  Both of the players. 

  1. The Two Water Jugs

This one is a medium-level interview puzzle that might appear in any interview selection process. 

Imagine you are at a riverside and given a 3-liter and a 5-liter jug, and initially, both of these jugs are empty. The jugs also do not have any markings to allow you to measure smaller quantities. You have to use these jugs and measure 4 liters of river water. 

Determine the minimum number of operations you must perform to obtain 4 liters in one of the jugs. Here is a limitation of operation you can perform. 

  • You can empty a jug
  • You can fill a jug
  • You can put water by using one jug to fill the other until one of the jugs is either full or empty. 
  1. The Monkey & the Coconut

A monkey and five men find themselves on a deserted island after a shipwrecking incident. On the first day, they gather coconuts for food. They pile these coconuts together and then go to sleep during the nighttime. 

While they were all fast asleep, one of them woke up and thought everyone might have a row in the morning to divide the coconuts. So he decides to separate and take his share of coconuts. He divides the whole pile into five portions. In the end, he has a single coconut as a leftover, so he decides to give it to the monkey. Later he hides his pile and puts the rest of the coconuts back in a pile together. 

The night goes on, and each of the five men wakes up one after another and does the same exercise. Each of them makes five piles from the remaining pile, takes their individual share, and gives one remaining coconut to the monkey. 

In the morning, they divide the remaining coconuts amongst themselves and again giving one coconut to the monkey for one last time. 

Now you have to find out the minimum number of total coconuts that were in the original pile. 

  1. The Einstein’s Puzzle 

A riddle in the mix but a hard one that will get you scratching your skull. Dare to try? 

Let us imagine that you have five houses of five different colors in front of you. They are all on the same road and next to each other. Now, in each of these houses lives a man belonging to a different country. Each of these men has their favorite drinks, their favorite cigarette brand, and each keeps a particular kind of pet. 

  • The first is the red house, and an Englishman lives in it. 
  • The Swede has a pet dog
  • The Dane guy drinks tea
  • The green house is right next to the white house
  • The owner of the green house loves to drink coffee
  • The guy smoking the Pall Mall has possession of birds
  • The yellow house owner smokes Dunhill
  • The owner of the house in the center drinks milk
  • The Norwegian guy lives in the very first house
  • The blend smoker guy has a neighbor with pet cats
  • The man who loves to smoke Blue Masters also drinks beer. 
  • The man with pet horses lives next to the guy who smokes Dunhill
  • The German man smokes Prince
  • The Norwegian man lives right next to the house in blue
  • The blend smoker is a neighbor to the guy who drinks water. 

The question for you is, and get ready for this one….Who keeps the Fish? 

Your options are: 

Option 1: The Dane

Option 2: The Englishman

Option 3: The German

Option 4: The Swede

Option 5: The Norwegian

  1. Six Colored Cube

This easy mathematical interview puzzle will help you grow in confidence and learn basic problem-solving skills. 

You have six distinct colors. Your task is to determine the number of unique ways you can paint a six-faced cube in such a way that no two faces are of the same color? Remember that you cannot mix the colors. 

  1. 3 Mislabeled Jars

Imagine you have three jars with the wrong labels on them. One of them has peanut butter jellybeans. The second one has grape jellybeans, and the third contains a mix of both types of jellybeans (not in equal quantity necessarily). 

Your job is to determine the minimum amount of jellybeans you would require to pull out to fix the label on each of the jars. The labels on each jar are 

Jar 1: peanut butter

Jar 2: grapes

Jar 3. P.B/Grape

  1. Prisoners and Poison

There is a bad king with a cellar containing 1000 bottles of expensive and delightful wine. A queen of the neighboring state plots to kill this bad king, so she sends one of her servants to poison the king’s wine. 

Call it bad king’s luck; the guards of the castle catch this servant after he has poisoned just one bottle. However, the guards have no clue which one bottle out of the 1000 bottles has this servant poisoned. However, they know that the poison is potent enough that even diluting it 100,000 times will still kill the king. Moreover, the poison takes a month to show any effect. 

Now, the kind decides to use some of the prisoners from a vast dungeon to test the wine. He is a clever bad king, so he wants to murder as a small number of prisoners as he possibly can. The idea is to weed out that single bottle of poisoned wine with a low prisoner death rate so he can enjoy the 999 bottles at his anniversary in 5 weeks' time. 

Let us take the worst-case scenario; what do you think will be the minimum number of dungeon prisoners the bad would need to kill to find the poisoned wine bottle? 

Do remember, the king wants to kill as few prisoners as possible during this experiment. He may even decide to kill all the prisoners participating in this experiment in case he feels that they may reveal his evil plans to all. 

  1. Truth & Lie

There are two tribes on Mars, a Lie tribe and a Truth Tribe. The Lie tribe people only and always speak a lie, whereas the True tribe only speaks the truth. You come across three Martian people and ask from the very first one. 

Question: which of the tribe are you from? 

The person replies in his language, but you do not understand it. The second one tells you that the first one is saying that he belongs to the Lie tribe. The third person tells you that the second person is actually lying. 

So, which tribe does this third person belong to? 

Option1: Lie Tribe

Option2: True Tribe

Option 3: You cannot say

  1. The Next Number

10, 9, 60, 90, 70, 66, 96, 94, 98…?

Your task is to figure out the number that will come next in this sequence. 

  1. Wolf-Goat-Cabbage

This is probably one of the easy ones when it comes to the top 20 puzzles for interviews. It is more of a riddle and does not require any numerical solutions. 

There is a farmer by the riverside, and he wishes to cross the river. However, he is not alone and has a wolf, a goat, and a cabbage with him. Now, he only has one boat at his disposal, which can support a farmer along with one more companion, i.e., wolf, goat, or cabbage. 

However, the problem farmer faces is that whether he leaves the goad and wolf alone by the shore or in the boat, the wolf is going to eat the goat. Similarly, if he leaves the goat and cabbage by the shore or on the boat, the goat is going to eat the cabbage. 

What is the minimum number of tips the farmer must make to get everything safely to the other side? Crossing the river counts a single trip. So, time to get your thinking hat on.

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