31 lines
818 B
PHP
31 lines
818 B
PHP
<?php
|
|
|
|
[$template, $rules] = explode("\n\n", file_get_contents('./input.txt'));
|
|
|
|
$template = str_split($template);
|
|
|
|
$pair_insertion_rules = [];
|
|
foreach (explode("\n", $rules) as $rule) {
|
|
[$key, $value] = explode(' -> ', $rule);
|
|
$pair_insertion_rules[$key] = $value;
|
|
}
|
|
|
|
for ($i = 0; $i < 40; $i++) {
|
|
$tmp = [];
|
|
foreach ($template as $i_char => $char) {
|
|
if (array_key_exists($i_char+1, $template)) {
|
|
$tmp[] = $char;
|
|
$pair = $char . $template[$i_char + 1];
|
|
if (array_key_exists($pair, $pair_insertion_rules)) {
|
|
$tmp[] = $pair_insertion_rules[$pair];
|
|
}
|
|
}
|
|
}
|
|
$tmp[] = array_pop($template);
|
|
$template = $tmp;
|
|
echo $i."\n";
|
|
}
|
|
|
|
$count_char = array_count_values($template);
|
|
echo max($count_char) - min($count_char);
|