2024: day 13 part 2

plagov · Dec 20, 2024 · 777535d · 777535d
1 parent fef8580
commit 777535d
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Showing 2 changed files with 29 additions and 11 deletions.
diff --git a/src/main/kotlin/io/plagov/advent/aoc2024/Day13.kt b/src/main/kotlin/io/plagov/advent/aoc2024/Day13.kt
@@ -7,23 +7,36 @@ class Day13 {
   private val buttonACost = 3
   private val buttonBCost = 1
 
-  fun partOne(input: String): Int {
-    val blocks = input.split("\n\n")
+  fun partOne(input: String): Long {
+    val totalCost = input.split("\n\n")
       .map { block -> parseBlock(block) }
       .map { clawMachine ->  calculate(clawMachine) }
       .sumOf { cost -> cost ?: 0 }
 
-    return blocks
+    return totalCost
   }
 
-  private fun calculate(clawMachine: ClawMachine): Int? {
+  fun partTwo(input: String): Long {
+    val prizeLocationOffset = 10000000000000L
+    val totalCost = input.split("\n\n")
+      .map { block -> parseBlock(block) }
+      .map { clawMachine ->  calculate(clawMachine, prizeLocationOffset) }
+      .sumOf { cost -> cost ?: 0 }
+
+    return totalCost
+  }
+
+  private fun calculate(clawMachine: ClawMachine, prizeLocationOffset: Long = 0): Long? {
     val (buttonA, buttonB, prize) = clawMachine
 
-    val pressACunt = (prize.x * buttonB.y - prize.y * buttonB.x) / (buttonA.x * buttonB.y - buttonA.y * buttonB.x)
-    val pressBCount = (buttonA.x * prize.y - buttonA.y * prize.x) / (buttonA.x * buttonB.y - buttonA.y * buttonB.x)
+    val prizeX = prize.x + prizeLocationOffset
+    val prizeY = prize.y + prizeLocationOffset
+
+    val pressACunt = (prizeX * buttonB.y - prizeY * buttonB.x) / (buttonA.x * buttonB.y - buttonA.y * buttonB.x)
+    val pressBCount = (buttonA.x * prizeY - buttonA.y * prizeX) / (buttonA.x * buttonB.y - buttonA.y * buttonB.x)
 
-    if (pressACunt * buttonA.x + pressBCount * buttonB.x == prize.x &&
-      pressACunt * buttonA.y + pressBCount * buttonB.y == prize.y) {
+    if (pressACunt * buttonA.x + pressBCount * buttonB.x == prizeX &&
+      pressACunt * buttonA.y + pressBCount * buttonB.y == prizeY) {
       val totalCost = pressACunt * buttonACost + pressBCount * buttonBCost
 
       return totalCost
@@ -45,15 +58,15 @@ class Day13 {
     )
 
     val prize = PrizeLocation(
-      x = match.groups["pricex"]?.value?.toInt()!!,
-      y = match.groups["pricey"]?.value?.toInt()!!
+      x = match.groups["pricex"]?.value?.toLong()!!,
+      y = match.groups["pricey"]?.value?.toLong()!!
     )
 
     return ClawMachine(buttonA, buttonB, prize)
 
   }
 
   data class Button(val x: Int, val y: Int)
-  data class PrizeLocation(val x: Int, val y: Int)
+  data class PrizeLocation(val x: Long, val y: Long)
   data class ClawMachine(val buttonA: Button, val buttonB: Button, val prize: PrizeLocation)
 }
diff --git a/src/test/kotlin/io/plagov/advent/aoc2024/Day13Test.kt b/src/test/kotlin/io/plagov/advent/aoc2024/Day13Test.kt
@@ -14,4 +14,9 @@ class Day13Test {
   fun partOne() {
     Assertions.assertEquals(28753, day13.partOne(input))
   }
+
+  @Test
+  fun partTwo() {
+    Assertions.assertEquals(102718967795500, day13.partTwo(input))
+  }
 }