Given an integer matrix, find a submatrix where the sum of numbers is zero. Your code should return the coordinate of the left-up and right-down number.
Given matrix
[
[1 ,5 ,7],
[3 ,7 ,-8],
[4 ,-8 ,9],
]
return [(1,1), (2,2)]
O(n3) time.
[LintCode] Submatrix Sum 子矩阵之和
原文：http://www.cnblogs.com/grandyang/p/5814131.html