✨ Add day 3 part 2

day_3/part_2.php

@@ -0,0 +1,41 @@
+<?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));