From eee724e1039111da60c2313a9fc5a8b757d38f0c Mon Sep 17 00:00:00 2001
From: Clement Desmidt <clement@desmidt.fr>
Date: Mon, 6 Dec 2021 16:47:24 +0100
Subject: [PATCH] :sparkles: Finit le jour 4

---
 day_4/part_2.php | 119 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 119 insertions(+)
 create mode 100644 day_4/part_2.php

diff --git a/day_4/part_2.php b/day_4/part_2.php
new file mode 100644
index 0000000..862e8d9
--- /dev/null
+++ b/day_4/part_2.php
@@ -0,0 +1,119 @@
+<?php
+
+// prepare numbers and grids
+$parts = explode("\n\n", file_get_contents('./input.txt'));
+
+$numbers = array_map('intval', explode(',', array_shift($parts)));
+
+$grids = array_map(static function($part) { return explode("\n", $part); }, $parts);
+
+array_walk_recursive($grids, static function (&$grid) {
+    if (is_string($grid)) {
+        $grid = array_map(static function($g) {
+            return 0;
+        }, array_flip(array_map('trim', str_split($grid, 3))));
+    }
+});
+
+/**
+ * Marks cell as done
+ *
+ * @param array $grids
+ * @param int   $number
+ */
+function modify_grids(array &$grids, int $number)
+{
+    foreach ($grids as $i_grid => $grid) {
+        foreach ($grid as $i_row => $row) {
+            foreach ($row as $cell => $cell_val) {
+                if ($cell === $number) {
+                    $grids[$i_grid][$i_row][$cell] = 1;
+                }
+            }
+        }
+    }
+}
+
+/**
+ * List all unmarked cell from a grid
+ *
+ * @param array $grid
+ *
+ * @return array
+ */
+function get_unmarked_from(array $grid): array
+{
+    $unmarked = [];
+    foreach ($grid as $row) {
+        $unmarked = array_merge($unmarked, array_keys(array_filter($row, static function($cell) {
+            return $cell === 0;
+        })));
+    }
+    return $unmarked;
+}
+
+/**
+ * Check if a grid is winning
+ *
+ * @param array $grids
+ *
+ * @return bool|array
+ */
+function check_grids(array &$grids): bool|array
+{
+    $result = false;
+
+    foreach ($grids as $i => $grid) {
+        if (check_lines($grid)) {
+            if (count($grids) === 1) return $grid;
+            unset($grids[$i]);
+            $result = true;
+        }
+        $rotated_grid = [];
+        $i = 0;
+        while (!empty($grid)) {
+            foreach ($grid as $j => $row) {
+                $rotated_grid[$i][array_key_last($row)] = array_pop($row);
+                $grid[$j] = $row;
+                if (empty($row)) unset($grid[$j]);
+            }
+            $i++;
+        }
+        if (check_lines($rotated_grid)) {
+            if (count($rotated_grid) === 1) return $grid;
+            unset($grids[$i]);
+            $result = true;
+        }
+    }
+
+    return $result;
+}
+
+/**
+ * Check if a line is all done
+ *
+ * @param array $grid
+ *
+ * @return bool|array
+ */
+function check_lines(array $grid): bool|array
+{
+    foreach ($grid as $row) {
+        if (array_sum($row) === 5) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
+foreach ($numbers as $number) {
+    modify_grids($grids, (int)$number);
+    $count = count($grids);
+    $test = check_grids($grids);
+    if ($count === 1 && $test) {
+        $grid = get_unmarked_from(is_array($test) ? $test : current($grids));
+        echo array_sum($grid) * $number;
+        break;
+    }
+}