class Solution {
    public int[][] diagonalSort(int[][] mat) {
        int m = mat.length;     //3
        int n = mat[0].length;   //4
        
        for(int k = 0; k < Math.min(m, n) ; k++){
            for(int i = 1; i < m; ++i){
                for(int j = 1; j < n; ++j){
                    if(mat[i][j] < mat[i-1][j-1]){
                        int temp = mat[i-1][j-1];
                        mat[i-1][j-1] = mat[i][j];
                        mat[i][j] = temp;
                    }
                }
            }
        }
        
        return mat;
    }
}