Solved day13 part 1

Author: Gentleman1983

build.gradle

@@ -4,7 +4,7 @@ plugins {
 
 // project meta data
 group 'de.havox_design.aoc2023'
-version '0.12.1'
+version '0.12.2'
 
 // Switch to gradle "all" distribution.
 wrapper {

day13/src/main/kotlin/de/havox_design/aoc2023/day13/Day13.kt

@@ -2,11 +2,24 @@ package de.havox_design.aoc2023.day13
 
 class Day13(private var filename: String) {
     fun solvePart1(): Long =
-        405L
+        makePatterns(getResourceAsText(filename))
+            .sumOf { it.mirrorValue() }
+            .toLong()
 
     fun solvePart2(): Long =
         0L
 
+    private fun makePatterns(input: List<String>): List<Pattern> {
+        return input
+            .withIndex()
+            .filter { (_, line) -> line.isEmpty() }
+            .map { it.index }
+            .let { listOf(-1) + it + (input.lastIndex + 1) }
+            .windowed(2)
+            .map { (before, after) -> input.subList(before + 1, after) }
+            .map(::Pattern)
+    }
+
     private fun getResourceAsText(path: String): List<String> =
         this.javaClass.classLoader.getResourceAsStream(path)!!.bufferedReader().readLines()
 }

day13/src/main/kotlin/de/havox_design/aoc2023/day13/Pattern.kt

@@ -0,0 +1,78 @@
+package de.havox_design.aoc2023.day13
+
+data class Pattern(val rows: List<String>) {
+    private val numColumns = rows[0].length
+
+    override fun toString(): String {
+        return rows
+            .joinToString("\n")
+    }
+
+    private fun column(index: Int): String {
+        return rows
+            .map { it[index] }
+            .joinToString("")
+    }
+
+    fun mirrorValue(pleaseDoNotBe: Int = 0): Int {
+        val rowScores = (0..<rows.lastIndex)
+            .filter(::isMirrorRow)
+            .map { (it + 1) * 100 }
+        val columnScores = (0..<numColumns)
+            .filter(::isMirrorColumn)
+            .map { it + 1 }
+
+        return (rowScores + columnScores)
+            .first { it != pleaseDoNotBe }
+    }
+
+    @SuppressWarnings("kotlin:S6510")
+    private fun isMirrorRow(index: Int): Boolean {
+        var top = index
+        var bottom = index + 1
+
+        when {
+            bottom > rows.lastIndex -> return false
+            else -> {
+                while (top >= 0 && bottom <= rows.lastIndex) {
+                    when {
+                        rows[top] != rows[bottom] -> {
+                            return false
+                        }
+
+                        else -> {
+                            top--
+                            bottom++
+                        }
+                    }
+                }
+                return true
+            }
+        }
+    }
+
+    @SuppressWarnings("kotlin:S6510")
+    private fun isMirrorColumn(index: Int): Boolean {
+        var left = index
+        var right = index + 1
+
+        when (right) {
+            numColumns -> return false
+            else -> {
+                while (left >= 0 && right < numColumns) {
+                    when {
+                        column(left) != column(right) -> {
+                            return false
+                        }
+
+                        else -> {
+                            left--
+                            right++
+                        }
+                    }
+                }
+                return true
+            }
+        }
+    }
+}