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 1:

Input: matrix = [[1,2,3,4],[5,1,2,3],[9,5,1,2]]
Output: True
Explanation:
1234
5123
9512

In the above grid, the diagonals are "[9]", "[5, 5]", "[1, 1, 1]", "[2, 2, 2]", "[3, 3]", "[4]", and 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:

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

Solution:

1. 

class Solution {
    public boolean isToeplitzMatrix(int[][] matrix) {
        if (matrix == null) {
            return true;
        }
        
        int rowSize = matrix.length, colSize = matrix[0].length;
        
        // identify the horizontal sequence 
        int i = 0;
        while (i < rowSize) {
            if (!isSame(matrix, i++, 0)) {
                return false;
            }
        }
        
        // identify the vertical sequence
        int j = 0;
        while (j < colSize) {
            if (!isSame(matrix, 0, j++)) {
                return false;
            }
        }
        
        return true;
    }
    
    private boolean isSame(int[][]matrix, int i, int j) {
        int rowSize = matrix.length, colSize = matrix[0].length;
        if (i >= rowSize || j >= colSize) {
            return true;
        }
        
        int benchMark = matrix[i++][j++];
        while (i < rowSize && j < colSize) {
            if (matrix[i++][j++] != benchMark) {
                return false;
            }
        }
        
        return true;
    }
}

2. 

class Solution {
    public boolean isToeplitzMatrix(int[][] matrix) {
        for (int i = 0; i < matrix.length - 1; i++) {
            for (int j = 0; j < matrix[0].length = 1; j++) {
                if (matrix[i][j] != matrix[i + 1][j + 1]) {
                    return false;
                }
            }
        }
        
        return true;
    }
}