A matrix is Toeplitz if every diagonal from top-left to bottom-right has the same elements. Given an `m x n` matrix, return `true` if it is Toeplitz. (Equivalently, check if each element equals the element up-left of it.)
2D list of ints.
Boolean.
Example 1:
Input:
matrix = [[1,2,3,4],[5,1,2,3],[9,5,1,2]]
Output:
true
Example 2:
Input:
matrix = [[1,2],[2,2]]
Output:
false
Example 3:
Input:
matrix = [[1]]
Output:
true