Day23 part1

days/src/main/kotlin/Day23.kt

@@ -0,0 +1,62 @@
+package be.vandewalleh.aoc.days
+
+import be.vandewalleh.aoc.utils.input.Day
+import be.vandewalleh.aoc.utils.input.Input
+import be.vandewalleh.aoc.utils.input.Text
+import be.vandewalleh.aoc.utils.input.createDay
+
+@Day(23)
+class Day23(@Text val input: Input<String>) {
+    private val cups = input.value.toCharArray().map { it.toString().toInt() }
+
+    fun part1() {
+        var cups = this.cups
+        var current = cups.first()
+
+        repeat(100) {
+            println("-- move ${it + 1} --")
+            val (newCurrent, newCups) = move(current, cups)
+            current = newCurrent
+            cups = newCups
+        }
+
+        println(cups.asSequence().infinite().dropWhile { it != 1 }.drop(1).take(cups.size - 1).joinToString(""))
+    }
+
+    private fun Sequence<Int>.infinite() = sequence { while (true) yieldAll(this@infinite) }
+
+    private fun move(current: Int, cups: List<Int>): Pair<Int, List<Int>> {
+        println("cups: ${cups.joinToString(" ").replace(current.toString(), "($current)")}")
+        val mutableCups = cups.toMutableList()
+
+        val picked = cups.asSequence().infinite().dropWhile { it != current }.drop(1).take(3).toList()
+        mutableCups.removeAll(picked)
+        println("pick up: ${picked.joinToString(", ")}")
+
+        fun chooseDestination(cups: List<Int>): Int {
+            val reordered = cups.asSequence().infinite().dropWhile { it != current }.take(mutableCups.size).toMutableList()
+            return reordered.filter { it < current }.maxOrNull() ?: reordered.maxOrNull()!!
+        }
+
+        val destinationCup = chooseDestination(mutableCups)
+
+        val out2 = mutableListOf<Int>()
+        for (cup in mutableCups) {
+            out2.add(cup)
+            if (cup == destinationCup) {
+                out2.addAll(picked)
+            }
+        }
+        val newCurrentCup = out2.asSequence().infinite().dropWhile { it != current }.drop(1).first()
+        return newCurrentCup to out2
+    }
+
+    fun part2() {
+
+    }
+}
+
+fun main() = with(createDay<Day23>("871369452")) {
+    println(part1())
+    println(part2())
+}

days/src/main/resources/day23.txt

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+871369452