Create a copy or use reference for parameter?

My problem is that I want to return a common substring of two strings s1, s2. Apparently, s1 and s2 are symmetric.

string shortest_common( const string& s1, const string& s2 ) {

}

There are three possible solutions to this problem that I came up with:

• Either make a copy of s1 and s2
• Or swap them, which means I have to sacrifi开发者_如何学编程ce their const-ness
• Or worst, duplicate code!

I personally prefer the first case, since intent is to find the shortest-common string not changing s1 or s2. So my question is: Which option is ideal in this case?

Thanks,

Chan

I would opt to go with the signature that you've displayed. If you're finding a common substring then you don't want to have side-effects. That's not what people think of when they would call your function. I don't expect a function called "add_two_numbers" to modify one of the numbers and return a value.

You could use recursion to swap the meanings of parameters without changing the objects themselves in any way.

I'm a bit confused as to what your actual question is, so I'll judge by the title.

Do both:

void shortest_common( string& s1, const string& s2 )
{
  // real algorithm changing s1
}

inline string shortest_common( string s1, const string& s2 )
{
  shortest_common( s1, s2 );
  return s1;
}