How to change a string's case based on another string?

Question

I'm working on a "Do you mean ..." kinda system similar to Google! The speller part is trivial (with PHP's pspell library) but what I can't solve is the case problem.

Let's say the mispelled word is "GoVeNMeNt" then the correct word should be "GoVerNMeNt" (similar to Google), but pspell library gives suggestions only in one-case (lower-case usually).

So how do I write a function transformCase which takes in the actual string ($string) and the suggestion string ($subject)? I have written the following implementation which doesn't handle all cases:

function transformCase($string,$subject){
    for ($i=0,$marker=0;$i<strlen($string);++$i)
        if (strcasecmp($string[$i],$subject[$marker])==0){
            $subject[$marker]=$string[$i];
            $marker+=1;
        }
        elseif (strlen($string)==strlen($subject))
            $marker+=1;
    return $subject;
}
echo transformCase("AbSaNcE",'absence')."\n";  # AbSeNcE :)
echo transformCase("StRioNG",'string')."\n";   # StRiNG  :)
echo transformCase("GOVERMENt",'government')."\n"; # GOVERNment :<

In the last case the output should be GOVERnMENt. The algorithm also doesn't work on various other queries.

So I'd be happy if someone helps me with the algorithm :)

Answer 1

Try the next modification to your algorithm:

function transformCase($string,$subject) {
    for ($i=0,$marker=0;$i<strlen($string);++$i) {
        if (strcasecmp($string[$i],$subject[$marker])==0) {
            $subject[$marker]=$string[$i];
            $marker+=1;
        }
        // Look for the next same character in $string
        while (strcasecmp($string[$i],$subject[$marker])!=0) {
            $i+=1;
        }
    }
    return $subject;
}

The comparisson elseif (strlen($string)==strlen($subject)) don't warrant the function to work as you need. Otherwise, you can introduce additional modifications for a best performance.