766. Toeplitz Matrix

问题：

给定一个二维数组，

若该数组的所有方向的对角线数值相同，则为Toeplitz矩阵，返回true，否则返回false

Example 1:
Input:
matrix = [
  [1,2,3,4],
  [5,1,2,3],
  [9,5,1,2]
]
Output: True
Explanation:
In the above grid, the diagonals are:
"[9]", "[5, 5]", "[1, 1, 1]", "[2, 2, 2]", "[3, 3]", "[4]".
In each diagonal all elements are the same, so the answer is True.

Example 2:
Input:
matrix = [
  [1,2],
  [2,2]
]
Output: False
Explanation:
The diagonal "[1, 2]" has different elements.

Note:
matrix will be a 2D array of integers.
matrix will have a number of rows and columns in range [1, 20].
matrix[i][j] will be integers in range [0, 99].

　　

解法：

i从1开始，j从1开始，

只要当前元素==[i-1] [j-1] （其左上角元素）一直到遍历结束，都满足，则满足条件。返回true。

只要其中一次不满足，则返回false

代码参考：

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