Run-length encoding

You are encouraged to solve this task according to the task description, using any language you may know.


Task

Given a string containing uppercase characters (A-Z), compress repeated 'runs' of the same character by storing the length of that run, and provide a function to reverse the compression.

The output can be anything, as long as you can recreate the input with it.



Example

 Input: WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW
 Output: 12W1B12W3B24W1B14W


Note: the encoding step in the above example is the same as a step of the Look-and-say sequence.




<?php
function encode($str)
{
    return preg_replace_callback('/(.)\1*/', function ($match) {
        return strlen($match[0]) . $match[1];
    }, $str);
}
 
function decode($str)
{
    return preg_replace_callback('/(\d+)(\D)/', function($match) {
        return str_repeat($match[2], $match[1]);
    }, $str);
}
 
echo encode('WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW'), PHP_EOL;
echo decode('12W1B12W3B24W1B14W'), PHP_EOL;
?>