Solution.js

/**
 * @param {number[][]} grid
 * @return {number}
 */
var cherryPickup = function (grid) {
    const n = grid.length;
    let dp = new Array(n * 2 - 1);
    for (let k = 0; k < dp.length; ++k) {
        dp[k] = new Array(n);
        for (let i = 0; i < n; ++i) {
            dp[k][i] = new Array(n).fill(-1e9);
        }
    }
    dp[0][0][0] = grid[0][0];
    for (let k = 1; k < n * 2 - 1; ++k) {
        for (let i1 = 0; i1 < n; ++i1) {
            for (let i2 = 0; i2 < n; ++i2) {
                const j1 = k - i1,
                    j2 = k - i2;
                if (
                    j1 < 0 ||
                    j1 >= n ||
                    j2 < 0 ||
                    j2 >= n ||
                    grid[i1][j1] == -1 ||
                    grid[i2][j2] == -1
                ) {
                    continue;
                }
                let t = grid[i1][j1];
                if (i1 != i2) {
                    t += grid[i2][j2];
                }
                for (let x1 = i1 - 1; x1 <= i1; ++x1) {
                    for (let x2 = i2 - 1; x2 <= i2; ++x2) {
                        if (x1 >= 0 && x2 >= 0) {
                            dp[k][i1][i2] = Math.max(dp[k][i1][i2], dp[k - 1][x1][x2] + t);
                        }
                    }
                }
            }
        }
    }
    return Math.max(0, dp[n * 2 - 2][n - 1][n - 1]);
};