There were two coding interviews. The interviews were on the same day, with different interviewers, and a 10-minute gap between them. The interviewers were really helpful. You had to write code on a whiteboard, so there was no way to compile the code. You had to compile the code in your brain.

Number of islands given a matrix containing 0s and 1s.

Follow up: An array of positions will be given that will convert water area to land. Count the number of islands for each conversion.

Given an integer n, return the least number of perfect square numbers that sum to n.