Day02

days/src/main/kotlin/Day02.kt

@@ -0,0 +1,29 @@
+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
+
+data class PasswordEntry(val range: IntRange, val letter: Char, val password: String)
+
+@Day(2)
+class Day02(@Lines input: Input<List<String>>) {
+    private val regex = "^(\\d+)-(\\d+) ([a-z]): (.*)$".toRegex()
+
+    private val passwords = input.value.map {
+        val (_, min, max, letter, password) = regex.find(it)!!.groupValues
+        PasswordEntry(min.toInt()..max.toInt(), letter[0], password)
+    }
+
+    fun part1() = passwords.count { it.password.count { char -> char == it.letter } in it.range }
+
+    fun part2() = passwords.count { (range, letter, pwd) ->
+        arrayOf(pwd[range.first -1], pwd[range.last - 1]).filter { it == letter }.size == 1
+    }
+}
+
+fun main() = with(createDay<Day02>()) {
+    println(part1())
+    println(part2())
+}