美团笔试还能这么问？正好看到今天学长在笔试，完全背包问题：

function fn (all) {
    const arr = [1, 5, 10, 20, 50, 100],
        len = arr.length,
        res = [];
    for (let i = 0; i <= len; i++) {
        res[i] = [];
        res[i][0] = 1;
    }
    for (let j = 1; j <= all; j++) {
        res[0][j] = 0;
    }
    for (let i = 1; i <= len; i++) {
        for (let j = 1; j <= all; j++) {
            res[i][j] = 0;
            for (let k = 0; k <= j / arr[i - 1]; k++) {
                res[i][j] += res[i - 1][j - k * arr[i - 1]];
            }
        }
    }
    return res[len][all];
}

还有美团的前端全是java，而且今天笔试比内推的算法要简单。