Coder's Cat

## LeetCode: 4Sum

2019-11-05

Solution for LeetCode 4sum

## Challenge Description

https://leetcode.com/problems/4sum/

Given an array nums of n integers and an integer target, are there elements a, b, c, and d in nums such that a + b + c + d = target? Find all unique quadruplets in the array which gives the sum of target.

Note:

The solution set must not contain duplicate quadruplets.

Example:

Given array nums = [1, 0, -1, 0, -2, 2], and target = 0.

A solution set is:

## Solution

For time optimization, we need to sort the given array. Then this problem transfered into the 3sum problem,

Time complexity is: $$O(N^3)$$

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