Find if given matrix is Toeplitz or not

题目地址：
http://www.geeksforgeeks.org/find-if-given-matrix-is-toeplitz-or-not/

题目：

Given a square matrix, find if it’s a Toeplitz matrix or not. A Toeplitz (or diagonal-constant) matrix is a matrix in which each descending diagonal from left to right is constant, i.e., all elements in a diagonal are same.

In general, any n×n matrix mat[][] is a Toeplitz matrix if every cell mat[i][j] is same as mat[i-1][j-1], mat[i+1][j+1], mat[i-2][j-2], mat[i+2][j+2], .. for every cell mat[i][j] and all the valid cells mat[i+k][j+k] or mat[i-k][j-k]

Examples :

Input: mat[N][N] = {{ 6, 7, 8},
                    { 4, 6, 7},
                    { 1, 4, 6}},
Output : True;
Values in all diagonals are same.

Input: mat[N][N] = {{ 6, 7, 8, 9 },
                    { 4, 6, 7, 8 },
                    { 1, 4, 6, 7 },
                    { 0, 1, 4, 6 },
                    { 2, 0, 1, 4 }};
Output : True;

Input: mat[N][N] = {{ 6, 3, 8},
                    { 4, 9, 7},
                    { 1, 4, 6}},
Output : False;

解题思路：

这道题就是一行一行的检查，只要有一个不对，马上返回FALSE；