day(05): solve part 1

Signed-off-by: Matej Focko <me@mfocko.xyz>

inputs/day05/sample.txt

@@ -0,0 +1,28 @@
+47|53
+97|13
+97|61
+97|47
+75|29
+61|13
+75|53
+29|13
+97|29
+53|29
+61|53
+97|53
+61|29
+47|13
+75|47
+97|75
+47|61
+75|61
+47|29
+75|13
+53|13
+
+75,47,61,53,29
+97,61,53,29,13
+75,29,13
+75,97,47,61,53
+61,13,29
+97,13,75,29,47

src/Day05.kt

@@ -0,0 +1,45 @@
+class Day05(
+    inputType: String,
+) : Day<Int, Int>() {
+    private val rules: Map<Int, MutableSet<Int>>
+    private val updates: List<List<Int>>
+
+    companion object {
+    }
+
+    init {
+        val (rules, updates) = readInputAsString(5, inputType).split("\n\n")
+
+        this.rules =
+            buildMap {
+                rules
+                    .lineSequence()
+                    .map { line ->
+                        line.split("|").map(String::toInt).let { it[0] to it[1] }
+                    }.forEach { (before, after) ->
+                        getOrPut(after) { mutableSetOf() }.add(before)
+                    }
+            }
+        this.updates = updates.lineSequence().map { line -> line.split(",").map(String::toInt).toList() }.toList()
+    }
+
+    override fun precompute() {
+        // no-op
+    }
+
+    private fun isCorrect(update: List<Int>): Boolean =
+        update.withIndex().reversed().all { p ->
+            rules.getOrDefault(p.value, mutableSetOf()).all { preceding -> update.lastIndexOf(preceding) < p.index }
+        }
+
+    override fun part1(): Int = updates.filter(::isCorrect).sumOf { it[it.size / 2] }
+
+    private fun fix(update: List<Int>): List<Int> = update
+
+    override fun part2(): Int = updates.filter { !isCorrect(it) }.map { fix(it) }.sumOf { it[it.size / 2] }
+}
+
+fun main() {
+    Day05("sample").test(143, 123)
+    Day05("input").run()
+}