Swapping two variables without using third variable
This is a very common interview question, esp. at the junior level. Let us first write a function that swap two integers using a third variable.
Prisoners and the lightbulb puzzle
There are 10 prisoners are in 10 different cells of a prison. There is no way in which they can communicate with each other. Each night, the warden picks one of the 10 prisoners and that prisoner is supposed to spend the entire night in the central living room. There is one bulb in the living […]
Logic Puzzle: Inverting the glasses
Four glasses are placed on the four corners of a square rotating table. Each glass is either upright (up) or upside-down (down). You have to turn all the glasses in same direction (either all up or all down). There are following conditions You are blindfolded, At one time you can only change two glasses (and […]
Interview Puzzle: Heaven or Hell
You are standing before two closed doors. One of the doors leads to heaven and the other one leads to hell. Two watchmen are standing, one in front of each door. You know one of them always tells the truth and the other always lies, but you don’t know which watchman tells the truth and who is the liar. […]
Gold bar puzzle
You have some work to be done by a worker in 7 days. The worker need to be paid every day after his work. The total cost of the work of 7 days is one gold bar (so every day the worker must be paid 1/7’th of the bar). You have only one gold bar, and […]
Points on globe – Interview puzzle
How many points are there on the globe, so that if you walk 1km south, then 1km east and then 1km north, you reach the place where you started.
Fastest horse Interview question
There are twenty five horses and you can conduct a race of only five horses at one time. There is no way to find out the absolute speed of a horse (we only know there relative speed). At least how many races will it take to determine the three fastest horses?
Count all left nodes in a Binary tree
One way to ask this question is: Given a Binary tree that represent a family hierarchy. A parent can have at most two children (at most one girl child and at most one boy child). A girl child (if present) is always represented as left child in the binary tree, and a boy child (if present) […]
5 Pirates Puzzle dividing 1000 coins
There are 5 pirates, A, B, C, D and E. They have a strict hierarchy, A is senior to B, B is senior to C, C is senior to D and D is senior to E. So it is like (A > B > C > D > E). These pirates have 1000 gold coins […]
Cheating Husband puzzle
A certain town has 100 married couples (husband and wife only). Everyone in the town lives by the following rule: If a husband cheats on his wife, the husband is executed (killed) as soon as his wife get to know out about him (He may enjoy only as long as his wife does not get to know about […]
