4th day

04/part1.php

@@ -0,0 +1,58 @@
+<?php
+
+$input = file('input', FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
+
+$numbers = explode(',', array_shift($input));
+$input = array_map(fn($line) => explode(' ', str_replace('  ', ' ', trim($line))), $input);
+$cards = array_chunk($input, 5);
+
+foreach ($numbers as $number) {
+    $cards = checkNumber($cards, $number);
+    if (($cardId = isWinner($cards)) !== false) {
+        echo calculateScore($cards[$cardId], $number);
+        break;
+    }
+}
+
+function calculateScore($card, $number)
+{
+    echo array_sum(array_map('array_sum', $card)) * $number;
+}
+
+function isWinner($cards)
+{
+    foreach ($cards as $cardIndex => $card) {
+        foreach ($card as $rowId => $cardRow) {
+            if (array_sum(array_column($card, $rowId)) === 0) {
+                return $cardIndex;
+            }
+            if (array_sum($cardRow) === 0) {
+                return $cardIndex;
+            }
+        }
+        $diagonal1 = $diagonal2 = false;
+        for ($i = 0; $i < 5; $i++) {
+            $diagonal1 += (int)$card[$i][$i];
+            $diagonal2 += (int)$card[$i][4 - $i];
+        }
+        if ($diagonal1 === 0) {
+            return $cardIndex;
+        }
+        if ($diagonal2 === 0) {
+            return $cardIndex;
+        }
+    }
+    return false;
+}
+
+function checkNumber($cards, $number)
+{
+    foreach ($cards as $cardIndex => $card) {
+        foreach ($card as $rowId => $cardRow) {
+            if (($index = array_search($number, $cardRow)) !== false) {
+                $cards[$cardIndex][$rowId][$index] = '';
+            }
+        }
+    }
+    return $cards;
+}