18. 4Sum
MediumTwo Pointers
Given an array nums of n integers, return an array of all the unique quadruplets [nums[a], nums[b], nums[c], nums[d]] such that: - 0 <= a, b, c, d < n - a, b, c, and d are distinct. - nums[a] + nums[b] + nums[c] + nums[d] == target You may return the answer in any order.
Examples
Input: [1,0,-1,0,-2,2] 0
Output: [[-2,-1,1,2],[-2,0,0,2],[-1,0,0,1]]
Explanation: Three unique quadruplets sum to 0.
Constraints
- 1 <= nums.length <= 200
- -10^9 <= nums[i] <= 10^9
- -10^9 <= target <= 10^9
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