"Tower of Hanoi" is a famous task. It has a simple recursive solution.

Today I'll show how to find a loop in linked list with a linear time complexity.

Some interview question can be solved by dynamic programming. One of such is a coin problem -
express an amount of money with the minimal coin number.

Another interesting task for interview is "Longest substring without repeating characters".

Usual interview task is: Print all possible n pairs of balanced parentheses.