They have three rounds of interviews. A candidate moves to the next round based on the feedback from the previous one. They mostly look for an exact solution and the corresponding code.

• Coding round
• Algorithms round
• Director interview (Design)

I could not get through the first round.

1. Given an unsorted array, find all possible pairs which sum to a given number with O(log n) complexity.

2. Given an array of strings, find all possible concatenations of strings. For example, for a, b, c, d the output should be ab, ac, ad, bc, bd, cd, abc, abd, acd, bcd.

3. Design a stack which will do push, pop, and min element operations in O(1) time.