Why does this program just print odds to the screen?

Question

#include <iostream>
using namespace std;

int main() {
for(int i = 0; i <= 15; i++)
if(i&1)
cout << i << endl;
return 0;
}

Answer 1

Your if statement is a faster odd test than:
if(i%2==1)

It does a bitwise and of the number i and 1. This results in 0 for evens or 1 for odds as both bits must be 1 to result in a 1. Any non-zero value is true so odds get printed.