I was asked this question - i didn't know the answer except the brute force method.

Given a matrix of size m x n - each element is either a 0 or 1. One has to find the largest X pattern marked by all 1s. The center of the X has to be 1 also - so we cannot have this as a X:

1 1

1 1

because the center of the X is not a 1 - just a blank. Can someone give clues as to how to do this faster.