add solution for 2023/day6

Author: libhide

src/main/kotlin/advent2023/Day06.kt

@@ -0,0 +1,46 @@
+package advent2023
+
+private const val COLON_DELIMITER = ":"
+
+class Day06(private val input: List<String>) {
+
+    fun solvePart1(): Int {
+        val times =
+            input.first().split(COLON_DELIMITER).last().split(" ").filter { it.isNotBlank() }.map { it.toLong() }
+        val distances =
+            input.last().split(COLON_DELIMITER).last().split(" ").filter { it.isNotBlank() }.map { it.toLong() }
+
+        val timeToDistance = times.mapIndexed { index, time ->
+            time to distances[index]
+        }.toMap()
+
+        val numberOfWays = computeNumberOfWaysToWin(timeToDistance)
+        return numberOfWays.reduce { acc, element -> acc * element }
+    }
+
+    fun solvePart2(): Int {
+        val time = input.first().split(COLON_DELIMITER).last().filter { it.isDigit() }.toLong()
+        val distance =
+            input.last().split(COLON_DELIMITER).last().filter { it.isDigit() }.toLong()
+        val timeToDistance = mapOf(time to distance)
+        val numberOfWays = computeNumberOfWaysToWin(timeToDistance)
+        return numberOfWays.reduce { acc, element -> acc * element }
+    }
+
+    private fun computeNumberOfWaysToWin(timeToDistance: Map<Long, Long>): List<Int> {
+        return timeToDistance.keys.map { time ->
+            (0..time).map { buttonHoldTime ->
+                buttonHoldTime * (time - buttonHoldTime)
+            }.count { distanceTravelled ->
+                distanceTravelled > (timeToDistance[time] ?: 0)
+            }
+        }
+    }
+}
+
+fun main() {
+    val input = Resources.resourceAsListOfString("advent2023/day06.txt")
+    val day06 = Day06(input = input)
+    println("Part 1 Solution: ${day06.solvePart1()}")
+    println("Part 2 Solution: ${day06.solvePart2()}")
+}

src/main/resources/advent2023/day06.txt

@@ -0,0 +1,2 @@
+Time:        46     80     78     66
+Distance:   214   1177   1402   1024

src/test/kotlin/advent2023/Day06Test.kt

@@ -0,0 +1,21 @@
+package advent2023
+
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+
+class Day06Test {
+
+    private val input = Resources.resourceAsListOfString("advent2023/day06.txt")
+
+    @Test
+    fun `test part 1`() {
+        val sut = Day06(input = input)
+        assertThat(sut.solvePart1()).isEqualTo(288)
+    }
+
+    @Test
+    fun `test part 2`() {
+        val sut = Day06(input = input)
+        assertThat(sut.solvePart2()).isEqualTo(71503)
+    }
+}

src/test/resources/advent2023/day06.txt

@@ -0,0 +1,2 @@
+Time:      7  15   30
+Distance:  9  40  200