4Sum--Find the 4 numbers in the array and the target

Given an array S of n integers, is there elements a, b, C, and D in S 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.

For example, given array S = [1, 0,-1, 0,-2, 2], and target = 0.A solution set is:[  [-1,  0, 0, 1],  [-2,- 1, 1, 2],  [-2,  0, 0, 2]]

classSolution { Public: Vector<vector<int>> Foursum (vector<int>& Nums,inttarget) {        intL =nums.size (), sum, left, right, I, J; Vector<vector<int>>ans; if(l<4)            returnans;        Sort (Nums.begin (), Nums.end ());  for(i =0; I<l-3; i++)        {            if(i && nums[i] = = nums[i-1])                Continue;  for(j = i +1; J<l-2; J + +)            {                if(nums[i]+nums[j]+nums[j+1]+nums[j+2]>target) Break; if(nums[i]+nums[j]+nums[l-2]+nums[l-1]<target)Continue; if(J>i +1&& Nums[j] = = Nums[j-1])                    Continue; Sum= Nums[i] +Nums[j]; Left= j +1; Right= L-1;  while(Left <Right ) {                    if(sum + nums[left] + nums[right] = =target) Ans.push_back ({nums[i], nums[j], Nums[left+ +], nums[right--] }); Else if(sum + nums[left] + Nums[right] <target) left++; Else Right--;  while(left>j+1&& Nums[left] = = Nums[left-1]) left++;  while(right<l-1&& Nums[right] = = Nums[right +1]) right--; }            }        }        returnans; }};

4Sum--Find the 4 numbers in the array and the target