Uva problem solution 10490 - Mr. Azad and his Son!!!!!

problem link:


Discuss: In this problem you have to use mathematical fact. if (2 power k − 1) is prime number then the number is perfect. or to check prime number you have to use the number n not the number generate by formula.


try yourself before see the code


#include<bits/stdc++.h>
#define ll long long
using namespace std;
int prime(ll n)
{

    int flag=0,i,j;
    for(i=2;i<=sqrt(n);i++)
    {
        if(n%i==0)
            flag=1;
    }
    if(!flag)
        return true;
        return false;
}
int main()
{

   ll n,i,j,m,perfect;
    while(cin >>n&&n!=0)
    {
        m=pow(2,n)-1;
        perfect=m*pow(2,n-1);
        i=prime(m);
        if(i)
            cout <<"Perfect: "<<perfect<<'!'<<endl;
        else
        {
            j=prime(n);
        if(j)
        cout <<"Given number is prime. But, NO perfect number is available."<<endl;
        else
            cout <<"Given number is NOT prime! NO perfect number is available."<<endl;
        }

    }
    return 0;
}