// https://leetcode.com/problems/toeplitz-matrix/
class Solution {
public:
bool isToeplitzMatrix(vector<vector<int>>& matrix) {
int m = matrix.size(), n = matrix[0].size();
for (int i = 1; i < m; ++i)
for (int j = 1; j < n; ++j)
if (matrix[i][j] != matrix[i - 1][j - 1]) return false;
return true;
}
};