Which one will execute faster, if (flag==0) or if (0==flag)?

Question

Interview question: Which one will execute faster, if (flag==0) or if (0==flag)? Why?

Answer 1

Which one's fast depends on which version of == you are using. Here's a snippet that uses 2 possible implementations of ==, and depending on whether you choose to call x == 0 or 0 == x one of the 2 is selected.

If you are just using a POD this really shouldn't matter when it comes to speed.

#include 
using namespace std;

class x { 
  public:
  bool operator==(int x) { cout << "hello\n"; return 0; }
  friend bool operator==(int x, const x& a) { cout << "world\n"; return 0; } 
};

int main()
{ 
   x x1;
   //int m = 0;
   int k = (x1 == 0);
   int j = (0 == x1);
}