From d0690ab93cb82efe575d77d117426ab2d5eafaa9 Mon Sep 17 00:00:00 2001
From: tchojnacki <tomaszchojnacki2001@gmail.com>
Date: Tue, 14 Dec 2021 12:16:23 +0100
Subject: Finish day 10

---
 README.md    |  6 ++---
 src/Day10.kt | 88 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 91 insertions(+), 3 deletions(-)
 create mode 100644 src/Day10.kt

diff --git a/README.md b/README.md
index 32a01b7..23b4fe7 100644
--- a/README.md
+++ b/README.md
@@ -1,7 +1,7 @@
 # Advent of Code 2021 in Kotlin
 ![Kotlin](https://img.shields.io/badge/Kotlin-grey?logo=Kotlin)
-![](https://img.shields.io/badge/⭐%20stars-18-yellow)
-![](https://img.shields.io/badge/📅%20days-9-blue)
+![](https://img.shields.io/badge/⭐%20stars-20-yellow)
+![](https://img.shields.io/badge/📅%20days-10-blue)
 
 Welcome to the Advent of Code[^aoc] Kotlin project created by [tchojnacki][github] using the [Advent of Code Kotlin Template][template] delivered by JetBrains.
 
@@ -17,7 +17,7 @@ Welcome to the Advent of Code[^aoc] Kotlin project created by [tchojnacki][githu
 | Day 7: The Treachery of Whales |   🌟   |   🌟   |
 | Day 8: Seven Segment Search    |   🌟   |   🌟   |
 | Day 9: Smoke Basin             |   🌟   |   🌟   |
-| Day 10: ???                    |        |        |
+| Day 10: Syntax Scoring         |   🌟   |   🌟   |
 | Day 11: ???                    |        |        |
 | Day 12: ???                    |        |        |
 | Day 13: ???                    |        |        |
diff --git a/src/Day10.kt b/src/Day10.kt
new file mode 100644
index 0000000..9985014
--- /dev/null
+++ b/src/Day10.kt
@@ -0,0 +1,88 @@
+enum class ChunkDelimeter(val open: Char, val close: Char) {
+    Parentheses('(', ')'),
+    Brackets('[', ']'),
+    Braces('{', '}'),
+    Angled('<', '>');
+
+    companion object {
+        fun isOpening(character: Char): Boolean = values().any { it.open == character }
+        fun isClosing(character: Char): Boolean = values().any { it.close == character }
+        fun from(character: Char): ChunkDelimeter = values().find { it.open == character || it.close == character }!!
+    }
+}
+
+sealed class SyntaxError {
+    object None : SyntaxError()
+    class IncompleteLine(private val stack: ArrayDeque<ChunkDelimeter>) : SyntaxError() {
+        val score: Long
+            get() {
+                fun delimeterValue(delimeter: ChunkDelimeter): Int = when (delimeter) {
+                    ChunkDelimeter.Parentheses -> 1
+                    ChunkDelimeter.Brackets -> 2
+                    ChunkDelimeter.Braces -> 3
+                    ChunkDelimeter.Angled -> 4
+                }
+
+                return stack.fold(0) { acc, elem -> acc * 5 + delimeterValue(elem) }
+            }
+    }
+    class CorruptedLine(private val invalidDelimeter: ChunkDelimeter) : SyntaxError() {
+        val score: Int
+            get() = when (invalidDelimeter) {
+                ChunkDelimeter.Parentheses -> 3
+                ChunkDelimeter.Brackets -> 57
+                ChunkDelimeter.Braces -> 1197
+                ChunkDelimeter.Angled -> 25137
+            }
+    }
+}
+
+fun parse(line: String): SyntaxError {
+    val stack = ArrayDeque<ChunkDelimeter>()
+
+    for (char in line) {
+        when {
+            ChunkDelimeter.isOpening(char) -> stack.addFirst(ChunkDelimeter.from(char))
+            ChunkDelimeter.isClosing(char) -> {
+                val closingDelimeter = ChunkDelimeter.from(char)
+                if (stack.first() == closingDelimeter) {
+                    stack.removeFirst()
+                } else {
+                    return SyntaxError.CorruptedLine(closingDelimeter)
+                }
+            }
+        }
+    }
+
+    if (stack.isNotEmpty()) {
+        return SyntaxError.IncompleteLine(stack)
+    }
+
+    return SyntaxError.None
+}
+
+fun main() {
+    fun part1(input: List<String>): Int = input
+        .map { parse(it) }
+        .filterIsInstance<SyntaxError.CorruptedLine>()
+        .sumOf { it.score }
+    
+    fun part2(input: List<String>): Long =
+        input
+            .asSequence()
+            .map { parse(it) }
+            .filterIsInstance<SyntaxError.IncompleteLine>()
+            .map { it.score }
+            .sorted()
+            .toList()
+            .let { it[it.size / 2] }
+
+
+    val testInput = readInputAsLines("Day10_test")
+    check(part1(testInput) == 26397)
+    check(part2(testInput) == 288957L)
+
+    val input = readInputAsLines("Day10")
+    println(part1(input))
+    println(part2(input))
+}
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