Add solution to day 6

src/Day06.kt

@@ -0,0 +1,60 @@
+fun main() {
+    fun part1(input: List<String>): Long = input.parseRaces()
+        .waysToWin()
+        .reduce { left, right -> left * right}
+
+    fun part2(input: List<String>): Long = input.parseRace().waysToWin()
+
+    // test if implementation meets criteria from the description, like:
+    val testInput = readInput("Day06_test")
+    check(part1(testInput) == 288L)
+
+    val input = readInput("Day06")
+    part1(input).println()
+    check(part2(testInput) == 71503L)
+    part2(input).println()
+}
+
+data class Race(val time: Long, val distance: Long)
+
+fun List<String>.parseRaces(): List<Race> {
+    val times = get(0).numbers()
+    val distances = get(1).numbers()
+    return times.zip(distances).map { Race(it.first, it.second) }.toList()
+}
+
+fun List<String>.parseRace(): Race {
+    val time = get(0).number()
+    val distance = get(1).number()
+    return Race(time, distance)
+}
+
+fun List<Race>.waysToWin(): List<Long> = map { race ->
+    race.waysToWin()
+}
+
+fun Race.waysToWin(): Long {
+    var min = 0L
+    for (pressTime in 1..<time) {
+        val moveTime = time - pressTime
+        val distanceMoved = moveTime * pressTime
+        if (distanceMoved > distance) {
+            min = pressTime
+            break
+        }
+    }
+    var max = 0L
+    for (pressTime in time downTo 1) {
+        val moveTime = time - pressTime
+        val distanceMoved = moveTime * pressTime
+        if (distanceMoved > distance) {
+            max = pressTime
+            break
+        }
+    }
+    return max - min + 1
+}
+
+fun String.numbers() = Regex("\\d+").findAll(this).map { it.value.toLong() }
+
+fun String.number() = Regex("\\d+").findAll(this).joinToString("") { it.value }.toLong()