Leetcode/leetcode18.cpp at main · ksaini-web/Leetcode · GitHub

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class Solution{
    public:

    vector<vector<int>> fourSum(vector<int>& nums,int target)
{

        vector<vector<int>>ans;
        int n=nums.size();

        if(n<4)return ans;

        sort(nums.begin(),nums.end());

        for(int i=0;i<n-3;i++){

            if( i>0&&nums[i]==nums[i-1]){
                continue;

            }

            for(int j=i+1;j<n-2;j++){

                if( j>i+1&&nums[j]==nums[j-1]){
                    continue;
                }
            int left=j+1,right=n-1;

            while(left<right){

                long long sum=(long long)nums[i]+nums[j]+nums[left]+nums[right];

                if(sum<target){
                    left++;

                }else if(sum>target){

                    right--;
                }

                else{
                    ans.push_back({nums[i],nums[j],nums[left],nums[right]});
                    left++;
                    right--;

                    while(left<right&&nums[left]==nums[left-1])
                    left++;
                    while(left<right&&nums[right]==nums[right+1])right--;
                }
            }
            }
        }
        return ans;
    }
};