2019-04-01-toeplitz matrix

题目，766. Toeplitz Matrix

A matrix is Toeplitz if every diagonal from top-left to bottom-right has the same element.

Now given an M x N matrix, return True if and only if the matrix is Toeplitz.

Example:
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.

解析

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var isToeplitzMatrix = function(matrix) {
  for (let i = 0; i < matrix.length; i++) {
    for (let j = 0; j < matrix[0].length; j++) {
      if (matrix[i+1] !== undefined && matrix[i+1][j+1] !== undefined) {
        if(matrix[i][j] !== matrix[i+1][j+1]) {
          return false;
        }
      }
    }
  }
  return true;
};