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

They should be exactly the same in terms of speed.

Notice however that some people use to put the constant on the left in equality comparisons (the so-called "Yoda conditionals") to avoid all the errors that may arise if you write = (assignment operator) instead of == (equality comparison operator); since assigning to a literal triggers a compilation error, this kind of mistake is avoided.

if(flag=0) // <--- typo: = instead of ==; flag is now set to 0
{
    // this is never executed
}

if(0=flag) // <--- compiler error, cannot assign value to literal
{

}

On the other hand, most people find "Yoda conditionals" weird-looking and annoying, especially since the class of errors they prevent can be spotted also by using adequate compiler warnings.

if(flag=0) // <--- warning: assignment in conditional expression
{

}