4sum.cpp

#include <bits/stdc++.h> 
using namespace std; 
void findFourElements(int arr[], int n, int X) 
{ 
	unordered_map<int, pair<int, int> > mp; 
	for (int i = 0; i < n - 1; i++) 
		for (int j = i + 1; j < n; j++) 
			mp[arr[i] + arr[j]] = { i, j };  
	for (int i = 0; i < n - 1; i++) 
    { 
		for (int j = i + 1; j < n; j++) 
        { 
			int sum = arr[i] + arr[j]; 
			if (mp.find(X - sum) != mp.end()) 
            { 
				pair<int, int> p = mp[X - sum]; 
				if (p.first != i && p.first != j 
					&& p.second != i && p.second != j) { 
					cout << arr[i] << ", "
						<< arr[j] << ", "
						<< arr[p.first] << ", "
						<< arr[p.second]; 
					return; 
				} 
			} 
		} 
	} 
} 

int main() 
{ 
	int n;
    cin>>n;
    int *arr = new int[n];
    for(int i = 0; i < n; ++i)
        cin>>arr[i];
    int X;
    cin>>X;    
	findFourElements(arr, n, X); 
	return 0; 
}