Maximal Square
Given a binary matrix, find out the largest size square sub-matrix with all 1's and return its area.
matrix = [[1, 0, 1, 0, 0], [1, 0, 1, 1, 1], [1, 1, 1, 1, 0], [1, 0, 0, 1, 0]]
4
The largest square is of size 2x2 and area 4.
m == matrix.lengthn == matrix[i].length1 <= m, n <= 300matrix[i][j]is0or1