From 51860c51167975dfc4afa505306c4326d5084314 Mon Sep 17 00:00:00 2001
From: Clement Desmidt <clement@desmidt.fr>
Date: Tue, 10 Dec 2019 15:07:47 +0100
Subject: [PATCH] :sparkles: Add day 10 part 1

---
 day_10/functions.php | 44 ++++++++++++++++++++++++++++++++++++
 day_10/part_1.php    | 54 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 98 insertions(+)
 create mode 100644 day_10/functions.php
 create mode 100644 day_10/part_1.php

diff --git a/day_10/functions.php b/day_10/functions.php
new file mode 100644
index 0000000..2dad4cd
--- /dev/null
+++ b/day_10/functions.php
@@ -0,0 +1,44 @@
+<?php
+
+
+/**
+ * @param array $array
+ * @return array|bool
+ */
+function array_flatten(array $array) {
+    return iterator_to_array(array_flatten_iterator($array), false);
+}
+
+/**
+ * @param array $array
+ * @return Generator
+ */
+function array_flatten_iterator(array $array) {
+    foreach ($array as $value) {
+        if (is_array($value)) {
+            yield from array_flatten_iterator($value);
+        } else {
+            yield $value;
+        }
+    }
+}
+
+/**
+ * @param int $x1
+ * @param int $y1
+ * @param int $x2
+ * @param int $y2
+ *
+ * @return array
+ */
+function getPointsBetween(int $x1, int $y1, int $x2, int $y2)
+{
+    $dx = $x2-$x1;
+    $dy = $y2-$y1;
+    $max = max(abs($dx), abs($dy));
+    for($t = 0; $t<=$max; $t++) {
+        $points[] = sprintf('%s,%s', $x1+($t*$dx)/$max, $y1+($t*$dy)/$max);
+    }
+
+    return $points;
+}
\ No newline at end of file
diff --git a/day_10/part_1.php b/day_10/part_1.php
new file mode 100644
index 0000000..f67bc51
--- /dev/null
+++ b/day_10/part_1.php
@@ -0,0 +1,54 @@
+<?php
+
+include 'functions.php';
+
+$rows = explode("\n", file_get_contents('input.txt'));
+
+// Make the list of asteroids coordinates
+$asteroids = array_flatten(
+    array_filter(
+        array_map(static function($row, $i) {
+            return array_filter(array_map(static function($col, $j) use ($i) {
+                if ($col === '#') {
+                    return sprintf('%s,%s', $i, $j);
+                }
+
+                return null;
+            }, str_split($row), range(0, strlen($row))));
+        }, $rows, range(0, count($rows)))
+    )
+);
+
+$asteroid_count = [];
+foreach ($asteroids as $asteroid_base) {
+    $count = 0;
+    foreach ($asteroids as $asteroid_target) {
+        if ($asteroid_base === $asteroid_target) {
+            continue;
+        }
+
+        $points_base = explode(',', $asteroid_base);
+        $points_target = explode(',', $asteroid_target);
+
+        $points = getPointsBetween($points_base[0], $points_base[1], $points_target[0], $points_target[1]);
+
+        $add_point = true;
+        foreach ($points as $point) {
+            if ($point === $asteroid_base || $point === $asteroid_target) {
+                continue;
+            }
+            if (in_array($point, $asteroids)) {
+                $add_point = false;
+                break;
+            }
+        }
+        if ($add_point) {
+            $count++;
+        }
+    }
+    $asteroid_count[$asteroid_base] = $count;
+}
+
+arsort($asteroid_count);
+var_dump($asteroid_count);
+echo current($asteroid_count);
\ No newline at end of file