string question

scialom

I have two string:
$s1 = "fyo";
$s2 = "fvbo";

I need to check if $s2 has the letters of $s2 but in the same order.

so in this case the result is true because $s2 has the letters on the same order of $s1.

I need to check hundreds of calculations on this kind of strings so I need rebuts solution.

Is it possible?
thanks

bradgrafelman

Since you can access characters in a string the same way you would elements in an array (e.g. using the square bracket notation, as if each character were in a numerical index starting from 0), one way might be to use a [man]for/man loop on string 1 to loop through each character one-by-one.

Inside the loop, you would have another loop that checks if the next character in string 2 matches the one you just read in string 1. If not, continue on to the next character in string 2 until you do find a match (or the string ends).

NogDog

Off the top of my head, so there may be bugs:

function whatever($str1, $str2)
{
  $chars = str_split($str1);
  foreach($chars as &$char) {
    $char = preg_quote($char);
  }
  $regexp = '/'.implode('.*', $chars).'/';
  return preg_match($regexp, $str2);
}

hsnopi

that is actually a classic Comp Sci problem. But yeah, I'd explode it into 2 arrays and do a nested foreach loop. Or you could use array_diff or array_intersec. PHP has great array functions.

bradgrafelman

Well since NogDog is giving away his tricks for free, I suppose I might as well follow suit:

function whatever($str1, $str2)
{
	for($i = 0, $j = 0; $i < strlen($str1) && $j < strlen($str2); $i++)
		while($j < strlen($str2) && $str1[$i] != $str2[$j++]);

return ($i == strlen($str1));
}