Toeplitz Matrix — C++

// Time:  O(m * n)
// Space: O(1)

class Solution {
public:
    bool isToeplitzMatrix(vector<vector<int>>& matrix) {
        for (int i = 0; i < matrix.size(); ++i) {
            for (int j = 0; j < matrix[i].size(); ++j) {
                if (i != 0 && j != 0 &&
                    matrix[i - 1][j - 1] != matrix[i][j]) {
                    return false;
                }
            }
        }
        return true;
    }
};