Answer to Question #306206 in C++ for oreo

Question

Given an integer n (between 1 and 104) find two prime numbers (possibly same) p1,p2 such that p1+p2=n

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

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

Answer 1

using namespace std;
/*
	Given an integer n (between 1 and 104) find two prime numbers (possibly same) p1,p2 such that p1+p2=n
	In case there are multiple solutions, you can output any of them.
	If there is no solution, then print -1 -1 instead.
*/


#define MAX	50
int is_prime(int n) 
{
  int i, Flag = 1;
  if (n == 0 || n == 1) Flag=0;
  else 
  {
    for(i = 2; i <= n/2; ++i) 
	{
      if(n % i == 0)  Flag = 0;
    }
  }
  return (Flag);
}


int main() 
{
	int n=0,Prime[MAX],m=50,c=0,r,u=-1,v=-1,Flag=0;
	m=0;
	while(m<1 || m>104)
	{
		cout<<"\nEnter a number between 1 and 104: "; cin>>m;
	}
  for(n=0;n<MAX;n++)Prime[n] = 0;
  	for(n=1;n<104;n++) 
  	{
		if(is_prime(n)==1) {Prime[c] = n;c++;}
  	}
	for(n=0;n<c;n++)
	{
		for(r=0;r<c;r++)
		{
			if(Prime[r]+Prime[c]==m)
			{
				Flag=1;
				u=Prime[r]; v = Prime[c];
				cout<<"\nPairs: "<<u<<", "<<v<<endl;
			}
		}
	}
	if(Flag==0) cout<<"\n\t-1 -1";
  return(0);
}