Sudoku Solver Problem Statement

You are provided with a 9x9 2D integer matrix MAT representing a Sudoku puzzle. The empty cells in the Sudoku are denoted by zeros, while the other cells contain integers from 1 to 9. Your task is to fill all empty cells so that the final matrix forms a valid Sudoku solution.

Example:

Input:

5 3 0 0 7 0 0 0 0
6 0 0 1 9 5 0 0 0
0 9 8 0 0 0 0 6 0
8 0 0 0 6 0 0 0 3
4 0 0 8 0 3 0 0 1
7 0 0 0 2 0 0 0 6
0 6 0 0 0 0 2 8 0
0 0 0 4 1 9 0 0 5
0 0 0 0 8 0 0 7 9

Output:

5 3 4 6 7 8 9 1 2
6 7 2 1 9 5 3 4 8
1 9 8 3 4 2 5 6 7
8 5 9 7 6 1 4 2 3
4 2 6 8 5 3 7 9 1
7 1 3 9 2 4 8 5 6
9 6 1 5 3 7 2 8 4
2 8 7 4 1 9 6 3 5
3 4 5 2 8 6 1 7 9

Explanation:

The given input matrix is filled such that each row, column, and 3x3 sub-grid contains all digits from 1 to 9 exactly once.

Constraints:

• The size of MAT is 9x9.
• 0 ≤ MAT[i][j] ≤ 9, where 0 indicates an empty cell.

Note:

You are not required to print anything, as it has already been taken care of. Just implement the function.