Find All Four Sum Numbers

// User function template for C++

// arr[] : int input array of integers
// k : the quadruple sum required
vector<vector<int> > fourSum(vector<int> &nums, int target) {
    vector<vector<int>> result;
        
    if(nums.empty())
        return result;
    
    sort(nums.begin(),nums.end());
    
    for(int i=0;i<nums.size();i++){
        for(int j=i+1;j<nums.size();j++){
            int target_2=target-nums[i]-nums[j];
            
            int front=j+1, back=nums.size()-1;
            while(front<back){
                int two_sum=nums[front]+nums[back];
                
                if(two_sum<target_2)
                    front++;
                else if(two_sum>target_2)
                    back--;
                else{
                    vector<int> quadruplet(4, 0);
                    quadruplet[0] = nums[i];
                    quadruplet[1] = nums[j];
                    quadruplet[2] = nums[front];
                    quadruplet[3] = nums[back];
                    result.push_back(quadruplet);
                
                    // Processing the duplicates of number 3
                    while(front<back && nums[front]==quadruplet[2]) ++front;
                
                    // Processing the duplicates of number 4
                    while(front<back && nums[back]==quadruplet[3]) --back;
                }
            }
            // Processing the duplicates of number 2
            while(j+1<nums.size() && nums[j+1]==nums[j]) ++j;
        }
        // Processing the duplicates of number 1
        while (i+1<nums.size() && nums[i+1]==nums[i]) ++i;
    }
    return result;
}