Pair of primes: PAIRPR1

                     

Contributor: Priya (CSE)

link: https://www.codechef.com/CU1AP0006/problems/PAIRPR1

Given an integer nn (between 11 and 104104) find two prime numbers (possibly same) p1,p2p1,p2 such that p1+p2=np1+p2=n

In case there are multiple solutions, you can output any of them.

If there is no solution, then print -1 -1 instead.

Solution:

#include <bits/stdc++.h>
#define endl "\n"
#define ll long long int
using namespace std;

ll T = 1;

bool isPrime(ll n)
{
    for (ll i = 2; i*i <= n ; i++)
    {
        if (n % i == 0)
            return false;
    }

    return true;
}

int solve()
{
    ll n;
    cin >> n;
    if (n <= 3)
    {
        cout << -1 << " " << -1 << endl;
        return 0;
    }
    for (int i = 2; i <= n/2 ; i++)
    {
        
       if (isPrime(i) && isPrime(n - i))
        {
            cout << i << " " << n - i << endl;
            return 0;
        }
    }
    cout << -1 << " " << -1 << endl;
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cin >> T;
    while (T--)
    {
        solve();
    }

    return 0;
}

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