
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 .
1 <= nums.length <= 200-10 ^9 <= nums[i] <= 10 ^9-10 ^9 <= target <= 10 ^9