<?php

$wire_paths = explode("\n", file_get_contents('input.txt'));
$wires = [];

function mark_wire_in_grid(string $wire)
{
    $steps = 0;
    $mapping = [
        'U' => [0,1],
        'D' => [0,-1],
        'L' => [-1,0],
        'R' => [1,0],
    ];
    $points = [];
    $path = explode(',', $wire);
    $current_point_x = 0;
    $current_point_y = 0;
    foreach ($path as $dot) {
        $direction = $dot[0];
        $number = (int) substr($dot, 1);
        for ($t = 0; $t < $number; $t++) {
            $current_point_x += $mapping[$direction][0];
            $current_point_y += $mapping[$direction][1];
            $points["$current_point_x,$current_point_y"] = ++$steps;
        }
    }

    return $points;
}

foreach ($wire_paths as $i => $wire_path) {
    $wires[] = mark_wire_in_grid($wire_path);
}

$common_points = array_intersect_key($wires[0], $wires[1]);
$total_steps = [];
foreach ($common_points as $coordinates => $steps) {
    $total_steps[$coordinates] = $wires[0][$coordinates] + $wires[1][$coordinates];
}
echo sprintf('Le plus court pas : %s', min($total_steps));