Given an array of integers `nums` and an integer `target`, return all unique quadruplets [nums[a], nums[b], nums[c], nums[d]] such that they sum to `target`. The solution set must not contain duplicate quadruplets.
nums = array of integers, target = integer target sum
list of unique quadruplets that sum to target
Example 1:
Input:
nums = [1,0,-1,0,-2,2] target = 0
Output:
[[-2,-1,1,2],[-2,0,0,2],[-1,0,0,1]]
Explanation:
All unique quadruplets.
Example 2:
Input:
nums = [2,2,2,2,2] target = 8
Output:
[[2,2,2,2]]
Explanation:
Only quadruplet [2,2,2,2] sums to 8.