Question

In the following two versions of switch case, I am wondering which version is efficient.

1:

string* convertToString(int i)
{
    switch(i)
    {
    case 1:
        return new string("one");
    case 2:
        return new string("two");
    case 3:
        return new string("three");
        .
        .
    default:
        return new string("error");
    }
}

2:

string* convertToString(int i)
{
    string *intAsString;
    switch(i)
    {
    case 1:
        intAsString = new string("one");
        break;
    case 2:
        intAsString = new string("two");
        break;
    case 3:
        intAsString = new string("three");
        break;
        .
        .
    default:
        intAsString = new string("error");
        break;
    }
return intAsString;
}

1: has multiple return statements will it cause compiler to generate extra code?

Answer 1

This is a premature optimization worry.

The former form is clearer and has fewer source lines, that is a compelling reason to chose it (in my opinion), of course.

You should (as usual) profile your program to determine if this function is even on the “hot list” for optimization. This will tell you if there is a performance penalty for using break.

As was pointed out in the comments, it’s very possible that the main performance culprit of this code is the dynamically allocated strings. Generally, when implementing this kind of “integer to string” mapping function, you should return string constants.