public class Solution
{
    public int[][] SortMatrix(int[][] grid)
    {
        // 左下
        var leftDiagonals = new Dictionary<int, List<int>>();
        for (var i = 0; i < grid.Length; i++)
        {
            // total -> 2n + 1 way
            for (var j = 0; j <= i; j++)
            {
                int diagonal = i - j;
                if (!leftDiagonals.ContainsKey(diagonal))
                {
                    leftDiagonals[diagonal] = new List<int>();
                }
                leftDiagonals[diagonal].Add(grid[i][j]);
            }
        }

        // 右上
        var rightDiagonals = new Dictionary<int, List<int>>();
        for (var i = 0; i < grid.Length; i++)
        {
            for (var j = i; j < grid.Length; j++)
            {
                int diagonal = j - i;
                if (!rightDiagonals.ContainsKey(diagonal))
                {
                    rightDiagonals[diagonal] = new List<int>();
                }
                rightDiagonals[diagonal].Add(grid[i][j]);
            }
        }

        foreach (var diagonal in leftDiagonals.Values)
        {
            diagonal.Sort((a, b) => b.CompareTo(a));
        }

        foreach (var diagonal in rightDiagonals.Values)
        {
            diagonal.Sort((a, b) => a.CompareTo(b));
        }

        for (var i = 0; i < grid.Length; i++)
        {
            for (var j = 0; j <= i; j++)
            {
                int diagonal = i - j;
                grid[i][j] = leftDiagonals[diagonal][0];
                leftDiagonals[diagonal].RemoveAt(0);
            }

            for (var j = i; j < grid.Length; j++)
            {
                if (i == j) continue;
                int diagonal = j - i;
                grid[i][j] = rightDiagonals[diagonal][0];
                rightDiagonals[diagonal].RemoveAt(0);
            }
        }
        return grid;
    }
}

public class Solution2 {
    public int[][] SortMatrix(int[][] grid) {
        int n = grid.Length;

        for (int i = 0; i < n; i++) {
            List<int> tmp = new List<int>();
            for (int j = 0; i + j < n; j++) {
                tmp.Add(grid[i + j][j]);
            }
            tmp.Sort((a, b) => b.CompareTo(a));
            for (int j = 0; i + j < n; j++) {
                grid[i + j][j] = tmp[j];
            }
        }

        for (int j = 1; j < n; j++) {
            List<int> tmp = new List<int>();
            for (int i = 0; j + i < n; i++) {
                tmp.Add(grid[i][j + i]);
            }
            tmp.Sort();
            for (int i = 0; j + i < n; i++) {
                grid[i][j + i] = tmp[i];
            }
        }

        return grid;
    }
}

class Program
{
    static void Main()
    {
        var Solution = new Solution();

        var gird = new int[][] { [1, 7, 3], [9, 8, 2], [4, 5, 6] };
        var result = Solution.SortMatrix(gird);

        for (int i = 0; i < result.Length; i++)
        {
            for (int j = 0; j < result[i].Length; j++)
            {
                Console.Write(result[i][j] + " ");
            }
            Console.WriteLine();
        }
    }
}