I have been racking my brain at this for a few days and I seem to be stuck. I'm new to PHP so please forgive any sloppiness or errors.
Given a pattern, for example something like an email address "ab@?b?.ca" I need to replace any instance of '?' with all possible permutations from a set of characters 'a-e', '@', and '.'
This is what I have right now:
function permute($str, $ch, $i, $n, &$output) {
if ($i == $n) {
array_push($output, $str);
} else {
for ($x = $i; $x < $n; $x++) {
for ($y = 0; $y < count($ch); $y++) {
$str[$x] = $ch[$y];
permute($str, $ch, $i + 1, $n, $output);
}
}
}
}
# each ? in the pattern to be replaced by all possible permutations of characters in chars array
# a through e as well as @ and .
$output = array();
$chars = range('a', 'e');
array_push($chars, '@');
array_push($chars, '.');
# the pattern to be checked
$pattern = "ab@?b?.ca";
permute($pattern, $chars, 0, strlen($pattern), $output);
... which is very close to what I want, but not quite correct. The function operates on every character of the string, but it should only do the work on the '?'s. Is there something else I can do that I'm missing? I will respond in a comment and edit if I figure this out!
Here is my working solution:
function permute($str, $arr, $i, $n, &$result) {
$nLen = strlen($n);
// cycle through every position of needle
while (($i = strpos($str, $n, $i)) !== false) {
$i = $i + $nLen;
// cycle through each replacement value
foreach ($arr as $value) {
$modified = substr_replace($str, $value, $i - $nLen, $nLen);
// if there are no needles left, save it
if (stristr($modified, $n) === false) {
$result[] = $modified;
}
permute($modified, $arr, $i, $n, $result);
}
}
}
# each ? in the pattern to be replaced by all possible permutations of characters in chars array
# a through e as well as @ and .
$chars = range('a', 'e');
array_push($chars, '@');
array_push($chars, '.');
# the pattern to be checked
$pattern = "ab@?b?.ca";
$result = array();
$needle = '?';
$index = 0;
permute($pattern, $chars, $index, $needle, $result);
var_dump($result);
This assumes that you only want to save values in which no needles remain. For example, instead of:
array(63) {
[0]=>
string(9) "ab@ab?.ca"
[1]=>
string(9) "ab@aba.ca"
[2]=>
string(9) "ab@abb.ca"
// etc...
It will output:
array(49) {
[0]=>
string(9) "ab@aba.ca"
[1]=>
string(9) "ab@abb.ca"
[2]=>
string(9) "ab@abc.ca"
// etc...
If you do in fact want the first result, then simply remove the stristr($modified, $n) === false
conditional.
This does the same thing without having to write out the algorithm:
$var = "ab@?b?.co";
$var = str_replace("?","",$var);
print $var;
//ab@b.co
Hope this helps.
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