Day05

2020-12-05 07:10:12 +01:00
parent 4008858df8
commit e65fbe9f63
3 changed files with 878 additions and 0 deletions
@@ -0,0 +1,50 @@
+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.Lines
+import be.vandewalleh.aoc.utils.input.createDay
+import kotlin.math.abs
+
+@Day(5)
+class Day05(@Lines val input: Input<List<String>>) {
+
+    private fun row(line: String) = line.take(7)
+        .replace("F", "0")
+        .replace("B", "1")
+        .let { Integer.parseInt(it, 2) }
+
+    private fun col(line: String) = line.takeLast(3)
+        .replace("L", "0")
+        .replace("R", "1")
+        .let { Integer.parseInt(it, 2) }
+
+    private fun id(seat: Pair<Int, Int>) = seat.first.times(8) + seat.second
+
+    fun part1() = input.value
+        .map { row(it) to col(it) }
+        .map { id(it) }
+        .maxOrNull()!!
+
+    fun part2(): Int {
+        val seats = input.value.map { row(it) to col(it) }
+
+        val front = seats.minByOrNull { it.first }!!.first
+        val back = seats.maxByOrNull { it.first }!!.first
+
+        return seats
+            .asSequence()
+            .filterNot { it.first == front }
+            .filterNot { it.first == back }
+            .map { id(it) }
+            .sorted()
+            .windowed(size = 2, step = 1)
+            .find { (a, b) -> abs(a - b) > 1 }!!
+            .first() + 1
+    }
+}
+
+fun main() = with(createDay<Day05>()) {
+    println(part1())
+    println(part2())
+}