day05

app/src/main/kotlin/day05/Day05.kt

@@ -0,0 +1,65 @@
+package day05
+
+import kotlin.io.println
+import kotlin.collections.listOf
+
+class Day05 {
+    fun parse(input: String): Pair<HashMap<Int, List<Int>>, List<List<Int>>> {
+        val (ruleStr, updateStr) = input.split("\n\n").map { it.lines() }
+        var rules = HashMap<Int, List<Int>>()
+        ruleStr.map {
+            val split = it.split("|").map { it.toInt() }
+            val cur = rules[split[0]] ?: listOf()
+            rules.set(split[0], cur + split[1])
+        }
+
+        val updates = updateStr.map { it.split(",").map { it.toInt() } }
+        return Pair(rules, updates)
+    }
+
+    fun part1(input: String): Int {
+        val (rules, updates) = parse(input)
+        return updates.filter {update -> checkOrder(rules, update) }
+            .map {update -> update[update.count() / 2] }
+            .sum()
+    }
+
+    fun checkOrder(rules: HashMap<Int, List<Int>>, update: List<Int>): Boolean {
+        for (i in 0..<update.count()) {
+            if (rules[update[i]]?.map { update.subList(0, i).contains(it) }?.contains(true) ?: false) {
+                return false
+            }
+        }
+        return true
+    }
+
+    fun fixOrder(rules: HashMap<Int, List<Int>>, update: List<Int>): List<Int> {
+        var modUpdate = update.toMutableList()
+        for (i in 0..<update.count()) {
+            val curPage = modUpdate[i]
+            val curRule = rules[curPage]
+            if (curRule == null) { continue }
+            for (pre in 0..<i) {
+                if (curRule.contains(modUpdate[pre])) {
+                    modUpdate[i] = modUpdate[pre]
+                    modUpdate[pre] = curPage
+                    break
+                }
+            }
+        }
+        // hate this but im lazy
+        if (!checkOrder(rules, modUpdate)) {
+            modUpdate = fixOrder(rules, modUpdate).toMutableList()
+        }
+        return modUpdate
+    }
+
+    fun part2(input: String): Int {
+        val (rules, updates) = parse(input)
+        return updates.filter {update -> !checkOrder(rules, update) }
+            .map { update -> fixOrder(rules, update) }
+            .map { update -> update[update.count() / 2] }
+            .sum()
+    }
+}
+

app/src/test/kotlin/day05/Day05Test.kt

@@ -0,0 +1,41 @@
+package day05
+
+import kotlin.test.Test
+import util.InputDownloader
+
+class Day05Test {
+    val dayNum = 5
+    val day = Day05()
+
+    val input = InputDownloader().getInput(dayNum)
+    val example = InputDownloader().getExample(dayNum)
+
+    @Test fun part1Example() {
+        part1(example, 143)
+    }
+
+    @Test fun part1Solution() {
+        part1(input, 6041)
+    }
+
+    @Test fun part2Example() {
+        part2(example, 123)
+    }
+
+    @Test fun part2Solution() {
+        part2(input, 4884)
+    }
+
+
+    fun part1(input: String, expected: Int) {
+        val output = day.part1(input)
+        println("output: $output")
+        assert(output == expected)
+    }
+
+    fun part2(input: String, expected: Int) {
+        val output = day.part2(input)
+        println("output: $output")
+        assert(output == expected)
+    }
+}