An element matrix[i][j] belongs to the same diagonal as matrix[i-1][j-1]. We just need to check if each element is equal to its top-left neighbor.

1. Iterate through i from 1 to m-1.
2. Iterate through j from 1 to n-1.
3. If matrix[i][j] != matrix[i-1][j-1], return False.
4. If loop finishes, return True.

• Time Complexity: O(M * N).
• Space Complexity: O(1).

def is_toeplitz_matrix(matrix):
    for i in range(1, len(matrix)):
        for j in range(1, len(matrix[0])):
            if matrix[i][j] != matrix[i - 1][j - 1]:
                return False
    return True