#Write a function called is_composite. is_composite should #take as input one integer. It should return True if the #integer is composite, False if the integer is not not #composite. You may assume the integer will be greater than #2 and less than 1000.

// A optimized school method based C++ program to check  

// if a number is composite.  

#include <bits/stdc++.h>  

using namespace std;  

bool isComposite(int n)  

{  

// Corner cases  

if (n <= 1) return false;  

if (n <= 3) return false;  

// This is checked so that we can skip  

// middle five numbers in below loop  

if (n%2 == 0 || n%3 == 0) return true;  

for (int i=5; i*i<=n; i=i+6)  

 if (n%i == 0 || n%(i+2) == 0)  

 return true;  

return false;  

}  

// Driver Program to test above function  

int main()  

{  

isComposite(11)? cout << " true\n": cout << " false\n";  

isComposite(15)? cout << " true\n": cout << " false\n";  

return 0;  

}

Explanation: