sort-matrix-by-diagonals

You are given an n x n square matrix of integers grid. Return the matrix such that:

• The diagonals in the bottom-left triangle (including the middle diagonal) are sorted in non-increasing order.


• The diagonals in the top-right triangle are sorted in non-decreasing order.

Example 1:

Input: grid = [[1,7,3],[9,8,2],[4,5,6]]

Output: [[8,2,3],[9,6,7],[4,5,1]]

Explanation:

The diagonals with a black arrow (bottom-left triangle) should be sorted in non-increasing order:

• [1, 8, 6] becomes [8, 6, 1].


• [9, 5] and [4] remain unchanged.

The diagonals with a blue arrow (top-right triangle) should be sorted in non-decreasing order:

• [7, 2] becomes [2, 7].


• [3] remains unchanged.

Example 2:

Input: grid = [[0,1],[1,2]]

Output: [[2,1],[1,0]]

Explanation:

The diagonals with a black arrow must be non-increasing, so [0, 2] is changed to [2, 0]. The other diagonals are already in the correct order.

Example 3:

Input: grid = [[1]]

Output: [[1]]

Explanation:

Diagonals with exactly one element are already in order, so no changes are needed.

Constraints:

• grid.length == grid[i].length == n


• 1 <= n <= 10


• -105 <= grid[i][j] <= 105