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Java-based LeetCode algorithm problem solutions, regularly updated

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454\. 4Sum II

Medium

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`

**Example 1:**

**Input:** nums1 = [1,2], nums2 = [-2,-1], nums3 = [-1,2], nums4 = [0,2]

**Output:** 2

**Explanation:** 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`
*   -2²⁸ <= nums1[i], nums2[i], nums3[i], nums4[i] <= 2²⁸