### 4Sum II

Given four lists A, B, C, D of integer values, compute how many tuples (i, j, k, l) there are such that Ai + Bj + Ck + Dl is zero.

To make problem a bit easier, all A, B, C, D have same length of N where 0 ≤ N ≤ 500. All integers are in the range of -2^28 to 2^28 - 1 and the result is guaranteed to be at most 2^31 - 1.

Example:

``````Input:
A = [ 1, 2]
B = [-2,-1]
C = [-1, 2]
D = [ 0, 2]

Output:
2

Explanation:
The two tuples are:
1. (0, 0, 0, 1) -> A[0] + B[0] + C[0] + D[1] = 1 + (-2) + (-1) + 2 = 0
2. (1, 1, 0, 0) -> A[1] + B[1] + C[0] + D[0] = 2 + (-1) + (-1) + 0 = 0``````

### Analyze

``````/**
* @param {number[]} A
* @param {number[]} B
* @param {number[]} C
* @param {number[]} D
* @return {number}
*/
var fourSumCount = function(A, B, C, D) {
const tmpMap = new Map()
for (let ic = 0; ic < C.length; ic++) {
for (let id = 0; id < D.length; id++) {
const sumC_D = C[ic] + D[id]
const hasSumC_D = tmpMap.has(sumC_D)
if (hasSumC_D) {
tmpMap.set(sumC_D, tmpMap.get(sumC_D) + 1)
} else {
tmpMap.set(sumC_D, 1)
}
}
}

let count = 0

for (let ia = 0; ia < A.length; ia++) {
for (let ib = 0; ib < B.length; ib++) {
const sumA_B = A[ia] + B[ib]
tmpMap.has(-sumA_B) && (count = count + tmpMap.get(-sumA_B))
}
}

return count
}``````

### Sister Title

18(题目相似, 但是因为传入参数不同导致解法不同)