Is this the best way to increment characters?

[wee493]

Currently I'm incrementing letters, for example aa, ab, ac ... az, ba. But I would like to make it so it goes aa, Aa, AA, aA, bb, Bb, BB... I'm halfway through making the code below, but I though I would ask if there is a better/easier way to do this? I would like to be able to support strings longer then 2 or three characters. Maybe a function or something?

 

$prev = 'aa';

// Capitalize fist letter if not and second letter not
if(!ctype_upper(substr($prev, 0, 1)) && !ctype_upper(substr($prev, 1, 2))){
$part_one = strtoupper(substr($prev, 0, 1));
$part_two = substr($prev, 1);
$prev = $part_one.$part_two;
}

// Un-Capitalize first letter if first and second are
if(ctype_upper(substr($prev, 0, 2))){
$part_one = strtolower(substr($prev, 0, 1));
$part_two = substr($prev, 1);
$prev = $part_one.$part_two;
}

// Capaitalize second letter if first is already
if(ctype_upper(substr($prev, 0, 1)) && !ctype_upper(substr($prev, 1, 2))){
$part_one = strtoupper(substr($prev, 0, 2));
$part_two = substr($prev, 2);
$prev = $part_one.$part_two;
}

echo $prev;

[gwolgamott]

It's small and clean. I see nothing wrong with that method. If you want to do a function then it's just dumping your code there into a function and returning an array to the main area you are using this would clean up the main code area if you liked.

[simshaun]

This could possibly be made more efficient, but I had to throw it together quickly.

<?php
echo "<pre>";
print_r(getLetterPermutations('a'));
echo "</pre>";

function getLetterPermutations($letter, $desiredLength = 2) {
$possiblePerms = pow(strlen($letter) * 2, $desiredLength);
$permutations = array($string = str_repeat($letter, $desiredLength));
$strlen = strlen($string);
for ($p = 1; $p <= $possiblePerms; $p++) {
	for ($x = 0; $x < $strlen; $x++) {
		$string[$x] = $string[$x] === strtoupper($string[$x]) ? strtolower($string[$x]) : strtoupper($string[$x]);
		if (!in_array($string, $permutations)) $permutations[] = $string;
	}
}

return $permutations;
}

[wee493]

This could possibly be made more efficient, but I had to throw it together quickly.

<?php
echo "<pre>";
print_r(getLetterPermutations('a'));
echo "</pre>";

function getLetterPermutations($letter, $desiredLength = 2) {
$possiblePerms = pow(strlen($letter) * 2, $desiredLength);
$permutations = array($string = str_repeat($letter, $desiredLength));
$strlen = strlen($string);
for ($p = 1; $p <= $possiblePerms; $p++) {
	for ($x = 0; $x < $strlen; $x++) {
		$string[$x] = $string[$x] === strtoupper($string[$x]) ? strtolower($string[$x]) : strtoupper($string[$x]);
		if (!in_array($string, $permutations)) $permutations[] = $string;
	}
}

return $permutations;
}

 

Thank you so much! I've made a few minor changes and adapted it to my need.

 

The efficiency is not a really problem, I most likely will never go over four characters as (if my math is correct) this should give me almost 3,000,000 unique results.

 

I'm getting better at PHP, just need to learn a little bit more about lines like this

$string[$x] = $string[$x] === strtoupper($string[$x]) ? strtolower($string[$x]) : strtoupper($string[$x]);

[Alex]

That's the ternary operator.