Toeplitz Matrix

Problem

Given an m x n matrix, return true if the matrix is Toeplitz. Otherwise, return false.

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

Constraints:

• m == matrix.length
• n == matrix[i].length
• 1 <= m, n <= 20
• 0 <= matrix[i][j] <= 99

Examples

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.

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

Solution

Iterate through each element in the matrix (starting from the second row and second column) and compare it with its top-left neighbor. If the matrix is Toeplitz, every element must equal its top-left neighbor along the same diagonal.

This approach requires only a single pass through the matrix to determine if it's a Toeplitz matrix.

Time Complexity: O(m × n), where m and n are the number of rows and columns. Space Complexity: O(1), using only constant extra space.

/**
 * @param {number[][]} matrix
 * @return {boolean}
 */
var isToeplitzMatrix = function (matrix) {
  const m = matrix.length
  const n = matrix[0].length

  for (let i = 1; i < m; i++) {
    for (let j = 1; j < n; j++) {
      if (matrix[i][j] !== matrix[i - 1][j - 1]) {
        return false
      }
    }
  }

  return true
}