力扣：741. 摘樱桃

不会做，想到死都想不出来，先CV再说，哈哈哈

class Solution {
    public int cherryPickup(int[][] grid) {
        int n = grid.length;
        int[][][] f = new int[2 * n - 1][n ][n];
        // 初始化数组为最小值，避免没有的情况
        for (int i = 0; i <  n * 2 - 1; i++){
            for (int j = 0; j < n; j++){
                Arrays.fill(f[i][j], Integer.MIN_VALUE);
            }
        }

        // 初始化
        f[0][0][0] = grid[0][0];
        for (int k = 1; k < 2 * n - 1; k++){
            for (int x1 = Math.max(k - n + 1, 0); x1 <= Math.min(k, n - 1); x1++){
                int y1 = k - x1;
                if (grid[x1][y1] == -1){
                    continue;
                }

                for (int x2 = x1; x2 <= Math.min(k, n - 1); x2++){
                    int y2 = k - x2;
                    if (grid[x2][y2] == -1){
                        continue;
                    }

                    int res = f[k - 1][x1][x2];// 都向右
                    if (x1 > 0){
                        res = Math.max(res, f[k - 1][x1 - 1][x2]);
                    }
                    if (x2 > 0){
                        res = Math.max(res, f[k - 1][x1][x2 - 1]);
                    }
                    if (x1 > 0 && x2 > 0){
                        res = Math.max(res, f[k - 1][x1 - 1][x2 - 1]);
                    }
                    res += grid[x1][y1];
                    if (x1 != x2){
                        res += grid[x2][y2];
                    }
                    f[k][x1][x2] = res;
                }
            }
        }
        return Math.max(f[n * 2 - 2][n - 1][n - 1], 0);
    }
}