Browsing the archives for the Puzzles category

Clock Hands

Question: How many times a day do the minute and hour hands of a clock overlap? Answer: Did you think the answer was 24 times? Well if you did, it’s time you think again. Let’s do some math. In T hours, the minute hand completes T laps. In the same amount of time, the hour hand […]


Piece of Cake

Question: How would you cut a rectangular cake into two equal pieces when a rectangular piece has already been cut out of it? The cut piece can be of any size and orientation. You are only allowed to make one straight cut. Answer: Simple question right? There are two possible solutions to this problem. People […]


Combinations of a String

Question: Write an algorithm to print all possible combinations of characters in a string. Answer: Any thoughts? One thing is for sure, we can definitely use some recursive logic here. Let’s approach this problem methodically. Since we need to generate combinations, we can start with a single character and then continue to add a character […]

Red, Green and Yellow Balls

Question: You are give two red balls, two green balls and two yellow balls. One ball from each color is heavier than the other one. All the heavier balls weigh the same and all the lighter balls weigh the same. You are only provided with a weighing balance. How many tries would it take to […]


Tunnel Trouble

Question: A man needs to go through a train tunnel to reach the other side. He starts running through the tunnel in an effort to reach his destination as soon as possible. When he is 1/4th of the way through the tunnel, he hears the train whistle behind him. Assuming the tunnel is not big […]

Farmer’s Dilemma

Question: A farmer bought a goat, a wolf and a cabbage from the market. On his way home, he has to cross a river. He has a small boat which only allows him to take one thing with him at a time. The farmer cannot leave the cabbage and the goat together (the goat would […]


Permutations of a String

Question: Print all the permutations of a string. Write code in C. Answer: Here is a recursive solution to print all the permutations of a string. However, this solution does not take care of duplicates. It is assumed that there are no duplicates in the string. I left out the implementation of the swap method […]

Three Switches

Question: You are standing outside a room next to three switches, all of which are off. Each switch operates a different light bulb in the room. The room door is closed, so you cannot see which switch operates which bulb. You are only allowed to go into the room once. Determine which switch operates which […]


Pick a Random Byte

Question: You have a stream of bytes from which you can read one byte at a time. You only have enough space to store one byte. After processing those bytes, you have to return a random byte. Note: The probability of picking any one of those bytes should be equal. Answer: Since we can only store […]

9 Minutes

Question: You are given two hourglasses. One measures 4 minutes and one measures 7 minutes. How would you measure exactly 9 minutes? Answer: This question is similar to 4 Quarts of Water. With water, we were able to fill and pour out the pail multiple times. We can use the same logic and easily come […]