4Sum II

arrayhash table

Problem Statement

Given four integer arrays nums1 , nums2 , nums3 , and nums4 all of length n , return the number of tuples (i, j, k, l) such that:

0 <= i, j, k, l < n

nums1[i] + nums2[j] + nums3[k] + nums4[l] == 0

Examples

Example 1

Input: nums1 = [1,2], nums2 = [-2,-1], nums3 = [-1,2], nums4 = [0,2]
Output: 2
The two tuples are:
1. (0, 0, 0, 1) -> nums1[0] + nums2[0] + nums3[0] + nums4[1] = 1 + (-2) + (-1) + 2 = 0
2. (1, 1, 0, 0) -> nums1[1] + nums2[1] + nums3[0] + nums4[0] = 2 + (-1) + (-1) + 0 = 0

Example 2

Input: nums1 = [0], nums2 = [0], nums3 = [0], nums4 = [0]
Output: 1

Constraints

n == nums1.length

n == nums2.length

n == nums3.length

n == nums4.length

1 <= n <= 200

-2 ^28 <= nums1[i], nums2[i], nums3[i], nums4[i] <= 2 ^28

🤔

Medium

Difficulty

Topic Info

ModuleDSA

CategoryArray

Sub-topicHash Table