Advent of Code: dag 5

<?php
require_once __DIR__ . '/../init.php';

$lines = array_filter($lines);

$first_line                   = $lines[0];
$the_numbers_we_need_to_check = explode(' ', explode(': ', $first_line)[1]);

$answer = PHP_INT_MAX;
foreach($the_numbers_we_need_to_check as $soil_number)
{
	$current_number = $soil_number;
	$mapping_found  = false;

	$mapping_lines  = array_slice($lines, 2);

	foreach($mapping_lines as $key => $line)
	{
		if(preg_match('/^[a-z]/', $line))
		{
			$mapping_found = false;
			continue;
		}

		if($mapping_found)
		{
			continue;
		}

		[$dest_start, $source_start, $steps] = explode(' ', $line);

		if($current_number < $source_start || $current_number > ($source_start + $steps))
		{
			$mapping_number = $current_number;
		}
		else
		{
			$difference     = $current_number - $source_start;
			$mapping_number = $dest_start + $difference;
			$current_number = $mapping_number;
			$mapping_found  = true;
		}
	}

	$answer = min($mapping_number, $answer);
}

printf("%d\n", $answer);

<?php

require_once __DIR__ . '/../init.php';

function splitRange(array $range_a, array $range_b): array
{
	$output = ['left' => [], 'center' => [], 'right' => []];

	if($range_a['min'] > $range_b['max'])
	{
		$output['right'] = $range_a;
	}

	elseif($range_a['max'] <= $range_b['min'])
	{
		$output['left'] = $range_a;
	}

	elseif($range_a['min'] >= $range_b['min'] && $range_a['max'] <= $range_b['max'])
	{
		$output['center'] = ['min' => $range_a['min'], 'max' => $range_a['max']];
	}

	elseif($range_a['min'] >= $range_b['min'] && $range_a['min'] <= $range_b['max'])
	{
		$output['center'] = ['min' => $range_a['min'], 'max' => $range_b['max']];
		$output['right']  = ['min' => $range_b['max'] + 1, 'max' => $range_a['max']];
	}

	elseif($range_a['min'] < $range_b['min'] && $range_a['max'] > $range_b['min'])
	{
		$output['left']   = ['min' => $range_a['min'], 'max' => $range_b['min'] - 1];
		$output['center'] = ['min' => $range_b['min'], 'max' => $range_a['max']];
	}

	return $output;
}

function extractSeedRanges(array $lines): array
{
	$seed_numbers = explode(' ', $lines[0]);
	$seed_ranges  = [];
	$iterations   = count($seed_numbers) - 1;

	for($i = 1; $i < $iterations; $i += 2)
	{
		$min           = $seed_numbers[$i];
		$max           = $min + $seed_numbers[$i + 1] - 1;
		$seed_ranges[] = ["min" => (int)$min, "max" => (int)$max];
	}

	usort($seed_ranges, fn($a, $b) => $a["min"] <=> $b["min"]);

	return $seed_ranges;
}

function createSectionMapping(string $section, array $map, array $lines, array $section_line_numbers): array
{
	if(!isset($section_line_numbers[$section]['to']))
	{
		$section_line_numbers[$section]['to'] = count($lines);
	}

	for($i = $section_line_numbers[$section]['from']; $i < $section_line_numbers[$section]['to']; $i++)
	{
		[$min_dest, $min_source, $steps] = array_map(fn($x) => (int)$x, explode(' ', $lines[$i]));

		$max_source = $min_source + $steps - 1;
		$max_dest   = $min_dest   + $steps - 1;

		$map[$section][] = [
			'source' => ['min' => $min_source	, 'max' => $max_source],
			'dest'   => ['min' => $min_dest		, 'max' => $max_dest],
			'shift'  => $min_dest - $min_source
		];
	}

	usort($map[$section], fn($a, $b) => $a['source']["min"] <=> $b['source']["min"]);
	return $map;
}

function buildMap($lines): array
{
	$line_count      = count($lines);
	$section_line_numbers              = [];
	$current_section = '';

	for($line_number = 2; $line_number < $line_count; $line_number++)
	{
		if(!preg_match('/(\w+-to-\w+) map:/', $lines[$line_number], $matches))
		{
			continue;
		}

		$section_line_numbers[$current_section]['to'] = $line_number - 1;
		$current_section                              = $matches[1];
		$map[$current_section]                        = [];
		$section_line_numbers[$current_section]       = ['from' => $line_number + 1];
	}

	foreach(array_keys($map) as $section)
	{
		$map = createSectionMapping($section, $map, $lines, $section_line_numbers);
	}

	return $map;
}

function transformRangesUsingMap($current_seed_ranges, $section, $map): array
{
	$current_intervals = $current_seed_ranges;
	$temp_intervals  = [];
	$new_intervals   = [];

	foreach(array_column($map[$section], 'source') as $k => $section_interval)
	{
		if(empty($current_intervals))
		{
			$current_intervals = $temp_intervals;
			$temp_intervals  = [];
		}

		while($current_source_range = array_shift($current_intervals))
		{
			$range_splits = splitRange($current_source_range, $section_interval);
			foreach($range_splits as $part => $split_range)
			{
				if(empty($split_range))
				{
					continue;
				}

				if($part == 'center')
				{
					$new_intervals[] = array_map(fn($x) => $x + $map[$section][$k]['shift'], $split_range);
				}
				else
				{
					$temp_intervals[] = $split_range;
				}
			}
		}
	}

	$output = array_merge($temp_intervals, $new_intervals);
	return $output;
}

function main(array $lines): void
{
	// start with the initial seed ranges
	$current_seed_ranges = extractSeedRanges($lines);
	$map             = buildMap($lines);
	$sections        = array_keys($map);

	foreach($sections as $k => $v)
	{
		$current_seed_ranges = transformRangesUsingMap($current_seed_ranges, $v, $map);
	}
	printf("%d\n", min(array_column($current_seed_ranges, 'min')));
}
main($lines);