Add day 8

src/Utils/Arr.php

@@ -1,8 +1,39 @@
 <?php
 
-namespace AdventOfCode21\Utils;
+namespace trizz\AdventOfCode\Utils;
 
 class Arr
 {
+    /**
+     * Flatten a multi-dimensional array into a single level.
+     *
+     * Based on:
+     *
+     * @see https://github.com/laravel/framework/blob/c16367a1af68d8f3a1addc1a819f9864334e2c66/src/Illuminate/Collections/Arr.php#L221-L249
+     *
+     * @param iterable  $array
+     * @param float|int $depth
+     *
+     * @return array
+     */
+    public static function flatten(iterable $array, float|int $depth = INF)
+    {
+        $result = [];
 
+        foreach ($array as $item) {
+            if (!is_array($item)) {
+                $result[] = $item;
+            } else {
+                $values = $depth === 1
+                    ? array_values($item)
+                    : static::flatten($item, $depth - 1);
+
+                foreach ($values as $value) {
+                    $result[] = $value;
+                }
+            }
+        }
+
+        return $result;
+    }
 }

src/Utils/Str.php

@@ -0,0 +1,35 @@
+<?php
+
+namespace trizz\AdventOfCode\Utils;
+
+class Str
+{
+    /**
+     * Check if the entirety of string two matches string one.
+     *
+     * @see https://github.com/MueR/adventofcode/blob/master/src/Util/StringUtil.php
+     */
+    public static function matchesAll(string $one, string $two): bool
+    {
+        for ($index = 0, $length = strlen($two); $index < $length; $index++) {
+            if (!str_contains($one, $two[$index])) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
+    /**
+     * Alphabetically sort characters in a string.
+     *
+     * @see https://github.com/MueR/adventofcode/blob/master/src/Util/StringUtil.php
+     */
+    public static function sort(string $string): string
+    {
+        $letters = array_unique(str_split($string));
+        sort($letters, SORT_STRING);
+
+        return implode('', $letters);
+    }
+}

src/Y21/Day8.php

@@ -0,0 +1,129 @@
+<?php
+
+namespace trizz\AdventOfCode\Y21;
+
+use trizz\AdventOfCode\Solution;
+use trizz\AdventOfCode\Utils\Arr;
+use trizz\AdventOfCode\Utils\Str;
+
+class Day8 extends Solution
+{
+    public static int|string|null $part1ExampleResult = 26;
+
+    public static int|string|null $part1Result = 397;
+
+    public static int|string|null $part2ExampleResult = 61229;
+
+    public static int|string|null $part2Result = 1027422;
+
+    private array $digitPatterns;
+
+    private array $patternDigits;
+
+    /**
+     * {@inheritdoc}
+     */
+    public function part1(array $data): int
+    {
+        $values = array_map(
+            static fn ($item) => strlen($item),
+            Arr::flatten(
+                array_map(
+                    static fn ($item) => explode(' ', $item),
+                    array_map(
+                        static fn ($item) => explode(' | ', $item)[1],
+                        $data
+                    )
+                )
+            )
+        );
+
+        return (count(array_intersect($values, [2, 4, 3, 7])));
+    }
+
+    public function part2(array $data): int|string
+    {
+        $sequences = [];
+
+        foreach ($data as $line) {
+            $item = explode(' | ', $line);
+            $sequences[] = [
+                'patterns' => array_map([Str::class, 'sort'], explode(' ', $item[0])),
+                'shown' => array_map([Str::class, 'sort'], explode(' ', $item[1])),
+            ];
+        }
+
+        $results = [];
+        foreach ($sequences as $sequence) {
+            $this->mapDigits($sequence['patterns']);
+            $output = '';
+
+            foreach ($sequence['shown'] as $pattern) {
+                $output .= $this->patternDigits[$pattern];
+            }
+
+            $results[] = (int) $output;
+        }
+
+        return array_sum($results);
+    }
+
+    /**
+     * @param array $patterns
+     *
+     * Code based on (sorry, didn't have a clue to solve this one, so I needed some inspiration):
+     *
+     * @see https://github.com/MueR/adventofcode/blob/master/src/AdventOfCode2021/Day08/Day08.php
+     */
+    public function mapDigits(array $patterns): void
+    {
+        /** @noinspection PackedHashtableOptimizationInspection */
+        $findDigit = [
+            // 1 is the only one with 2 segments
+            1 => static fn (string $pattern) => strlen($pattern) === 2,
+            // 7 is the only one with 3 segments
+            7 => static fn (string $pattern) => strlen($pattern) === 3,
+            // 4 is the only one with 4 segments
+            4 => static fn (string $pattern) => strlen($pattern) === 4,
+            // 8 is the only one with 7 segments
+            8 => static fn (string $pattern) => strlen($pattern) === 7,
+            // 9 is 6 segments, matches segments for 4
+            9 => fn (string $pattern) => strlen($pattern) === 6 && Str::matchesAll(
+                    $pattern,
+                    $this->digitPatterns[4] ?? ''
+                ),
+            // 0 is 6 segments, matching 1's segments (9 is already out)
+            0 => fn (string $pattern) => strlen($pattern) === 6 && Str::matchesAll(
+                    $pattern,
+                    $this->digitPatterns[1] ?? ''
+                ),
+            // 6 is 6 segments, the only one left
+            6 => static fn (string $pattern) => strlen($pattern) === 6,
+            // 3 is 5 segments and matches 1's segments
+            3 => fn (string $pattern) => strlen($pattern) === 5 && Str::matchesAll(
+                    $pattern,
+                    $this->digitPatterns[1] ?? ''
+                ),
+            // 5 is 5 segments, and 9 has all the segments of 5
+            5 => fn (string $pattern) => strlen($pattern) === 5 && Str::matchesAll(
+                    $this->digitPatterns[9] ?? '',
+                    $pattern
+                ),
+            // 2 is the only one remaining
+            2 => static fn (string $pattern) => true,
+        ];
+
+        foreach ($findDigit as $digit => $test) {
+            foreach ($patterns as $key => $pattern) {
+                if (!$test($pattern)) {
+                    continue;
+                }
+
+                unset($patterns[$key]);
+                $this->patternDigits[$pattern] = $digit;
+                $this->digitPatterns[$digit] = $pattern;
+                break;
+            }
+        }
+    }
+}