LeetCode: Finding Pairs With A Certain Sum Solution

1/**
2 * @param {number[]} nums1
3 * @param {number[]} nums2
4 */
5var FindSumPairs = function (nums1, nums2) {
6  this.nums1 = nums1
7  this.nums2 = nums2
8  this.occurences2 = nums2.reduce(
9    (acc, el) => acc.set(el, (acc.get(el) || 0) + 1),
10    new Map()
11  )
12}
13
14/**
15 * @param {number} index
16 * @param {number} val
17 * @return {void}
18 */
19FindSumPairs.prototype.add = function (index, val) {
20  const num = this.nums2[index]
21  const newNum = num + val
22  this.occurences2.set(num, this.occurences2.get(num) - 1)
23  this.occurences2.set(newNum, (this.occurences2.get(newNum) || 0) + 1)
24  this.nums2[index] = newNum
25}
26
27/**
28 * @param {number} tot
29 * @return {number}
30 */
31FindSumPairs.prototype.count = function (tot) {
32  let res = 0
33  for (const num1 of this.nums1) {
34    res += this.occurences2.get(tot - num1) || 0
35  }
36  return res
37}
38
39/**
40 * Your FindSumPairs object will be instantiated and called as such:
41 * var obj = new FindSumPairs(nums1, nums2)
42 * obj.add(index,val)
43 * var param_2 = obj.count(tot)
44 */