TwoSum.cpp

/* 
Given an integer array nums, return all the triplets [nums[i], nums[j], nums[k]] such that i != j, i != k, and j != k, and nums[i] + nums[j] + nums[k] == 0.

Input: nums = [-1,0,1,2,-1,-4]
Output: [[-1,-1,2],[-1,0,1]]

*/
#include<bits/stdc++.h>
using namespace std;

vector<vector<int>> threeSum(vector<int>& num) {
        vector<vector<int>> res; 
        sort(num.begin(), num.end()); 
        
        // moves for a
        for (int i = 0; i < (int)(num.size())-2; i++) {
            
            if (i == 0 || (i > 0 && num[i] != num[i-1])) {
                
                int lo = i+1, hi = (int)(num.size())-1, sum = 0 - num[i];
                
                while (lo < hi) {
                    if (num[lo] + num[hi] == sum) {
                        
                        vector<int> temp; 
                        temp.push_back(num[i]); 
                        temp.push_back(num[lo]); 
                        temp.push_back(num[hi]); 
                        res.push_back(temp);
                        
                        while (lo < hi && num[lo] == num[lo+1]) lo++;
                        while (lo < hi && num[hi] == num[hi-1]) hi--;
                        
                        lo++; hi--;
                    } 
                    else if (num[lo] + num[hi] < sum) lo++;
                    else hi--;
               }
            }
        }
        return res;
    }
int main(){
	int n;
	cout<<"Enter Size of array: ";
	cin>>n;
	int k;
	cout<<"Enter the target sum: ";
	cin>>k;
	cout<<"Enter the array elements: ";
	vector<int>arr(n);
	for(int i=0;i<n;i++)
		cin>>arr[i];
	vector<int>res=threeSum(arr);
	for(int i=0;i<res.size();i++)
			cout<<res[i][0]<<" "<res[i][1]<<" "<<res[i][2]<<endl;
}