LeetCode: Combination Sum IV Solution

1/**
2 * @param {number[]} nums
3 * @param {number} target
4 * @return {number}
5 */
6var combinationSum4 = function (nums, target) {
7  const recursion = (accumulatedSum, memo = new Map()) => {
8    if (memo.has(accumulatedSum)) {
9      return memo.get(accumulatedSum)
10    }
11
12    if (accumulatedSum > target) {
13      return 0
14    }
15
16    if (accumulatedSum === target) {
17      return 1
18    }
19
20    let res = 0
21    for (const num of nums) {
22      res += recursion(accumulatedSum + num, memo)
23    }
24    memo.set(accumulatedSum, res)
25
26    return res
27  }
28
29  return recursion(0)
30}