This question was asked by Zillow.
You are given a 2-d matrix where each cell represents number of coins in that cell. Assuming we start at matrix[0][0], and can only move right or down, find the maximum number of coins you can collect by the bottom right corner.
For example, in this matrix
0 3 1 1
2 0 0 4
1 5 3 1
The most we can collect is 0 + 2 + 1 + 5 + 3 + 1 = 12 coins.