aoc-23: solve day 6

advent-of-code-2023/src/main/kotlin/Solution06.kt

@@ -0,0 +1,66 @@
+import kotlin.math.ceil
+import kotlin.math.sqrt
+
+class Solution06(lines: List<String>) {
+    private val races = mutableListOf<Race>()
+
+    init {
+        val times = lines[0]
+            .replace("Time:", "")
+            .split(" ")
+            .filter{it.isNotEmpty()}
+        val records = lines[1]
+            .replace("Distance:", "")
+            .split(" ")
+            .filter{it.isNotEmpty()}
+
+        for (i in times.indices) {
+            races.add(
+                Race(records[i].toLong(), times[i].toLong())
+            )
+        }
+    }
+
+    fun getMultipliedNumbersOfWays(): Int {
+        var res = 1
+
+        println("races: $races")
+
+        for (race in races) {
+            var x1 = (race.duration - sqrt(race.duration * race.duration - 4.0 * race.distance)) / 2.0
+            val x2 = (race.duration + sqrt(race.duration * race.duration - 4.0 * race.distance)) / 2.0
+
+            if (ceil(x1) - x1 < 1e-4) {
+                x1 += 0.5
+            }
+
+            println("x1 = $x1, x2 = $x2")
+
+            res *= (ceil(x2) - ceil(x1)).toInt()
+        }
+
+        return res
+    }
+
+    fun getNumberOfWaysForOneRace(): Int {
+        val race = Race(
+            races.map{it.distance.toString()}.reduce{acc, s ->  acc + s}.toLong(),
+            races.map{it.duration.toString()}.reduce{acc, s ->  acc + s}.toLong(),
+        )
+
+        println("distance: ${race.distance}, duration: ${race.duration}")
+
+        var x1 = (race.duration - sqrt(race.duration * race.duration - 4.0 * race.distance)) / 2.0
+        val x2 = (race.duration + sqrt(race.duration * race.duration - 4.0 * race.distance)) / 2.0
+
+        if (ceil(x1) - x1 < 1e-4) {
+            x1 += 0.5
+        }
+
+        println("x1 = $x1, x2 = $x2")
+
+        return (ceil(x2) - ceil(x1)).toInt()
+    }
+}
+
+data class Race(val distance: Long, val duration: Long)

advent-of-code-2023/src/main/resources/day-06/input.txt

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+Time:        47     84     74     67
+Distance:   207   1394   1209   1014

advent-of-code-2023/src/main/resources/day-06/test.txt

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+Time:      7  15   30
+Distance:  9  40  200

advent-of-code-2023/src/test/kotlin/Solution06Test.kt

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+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class Solution06Test{
+
+    @Test
+    fun testGetMultipliedNumbersOfWays() {
+        val text = ResourceReader().readFile("day-06/test.txt")
+        val res = Solution06(text).getMultipliedNumbersOfWays()
+        assertEquals(288, res)
+    }
+
+    @Test
+    fun solvePart1() {
+        val text = ResourceReader().readFile("day-06/input.txt")
+        val res = Solution06(text).getMultipliedNumbersOfWays()
+        println(res)
+    }
+
+    @Test
+    fun testGetNumberOfWaysForOneRace() {
+        val text = ResourceReader().readFile("day-06/test.txt")
+        val res = Solution06(text).getNumberOfWaysForOneRace()
+        assertEquals(71503, res)
+    }
+
+    @Test
+    fun solvePart2() {
+        val text = ResourceReader().readFile("day-06/input.txt")
+        val res = Solution06(text).getNumberOfWaysForOneRace()
+        println(res)
+    }
+}