day 3 puzzle 2

2023-12-03 11:23:54 +01:00
parent 548fea505d
commit a9033f64e5
2 changed files with 113 additions and 0 deletions
--- a/src/day3/Puzzle2.scala
+++ b/src/day3/Puzzle2.scala
@@ -0,0 +1,104 @@
+package day3
+
+import scala.collection.mutable.ArrayBuffer
+import scala.io.{BufferedSource, Source}
+
+object Puzzle2 {
+  case class Number(x: Int, y: Int, value: Int, length: Int)
+  case class Gear(x: Int, y: Int, var ratio: Int = 1, var neighbours: Int = 0)
+
+  var width = 0
+  var height = 0
+
+  var schematic: Array[Array[Char]] = Array.empty
+  var numbers: ArrayBuffer[Number] = new ArrayBuffer()
+  var gears: ArrayBuffer[Gear] = new ArrayBuffer()
+
+  def loadInput(path: String): Unit = {
+    val source: BufferedSource = Source.fromFile(path)
+    val lines: Array[String] = source.getLines().toArray
+    height = lines.length
+    width = if (height == 0) 0 else lines(0).length
+    schematic = new Array(height)
+
+    var i = 0
+    for (line: String <- lines) {
+      schematic(i) = line.split("").map(s => s(0))
+      i += 1
+    }
+
+    source.close()
+  }
+
+  def getNumber(sx: Int, sy: Int): String = {
+    var x: Int = sx
+    var number: String = ""
+    var c: Char = schematic(sy)(sx)
+    do {
+      number += c
+      x += 1
+      if (x < width) c = schematic(sy)(x)
+    } while ('0' <= c && c <= '9' && x < width)
+    return number
+  }
+
+  def findNumbers(): Unit = {
+    var y: Int = 0
+    var x: Int = 0
+
+    while (y < height) {
+      while (x < width) {
+        val c: Char = schematic(y)(x)
+        if ('0' <= c && c <= '9') {
+          val number: String = getNumber(x, y)
+          numbers.addOne(Number(x, y, number.toInt, number.length))
+          x += number.length - 1
+        }
+        x += 1
+      }
+      y += 1
+      x = 0
+    }
+  }
+
+  def findGears(): Unit = {
+    for (y: Int <- 0 until height) {
+      for (x: Int <- 0 until width) {
+        if (schematic(y)(x) == '*') {
+          gears.addOne(Gear(x, y))
+        }
+      }
+    }
+  }
+
+  def computePowers(): Unit = {
+    for (gear: Gear <- gears) {
+      for (number: Number <- numbers) {
+        if (areNeighbours(gear, number)) {
+          gear.ratio *= number.value
+          gear.neighbours += 1
+        }
+      }
+    }
+  }
+
+  def areNeighbours(gear: Gear, number: Number): Boolean = {
+    if (gear.x > number.x + number.length) return false
+    if (gear.y > number.y + 1) return false
+    if (number.x > gear.x + 1) return false
+    if (number.y > gear.y + 1) return false
+    return true
+  }
+
+  def solve(path: String): Int = {
+    loadInput(path)
+    findNumbers()
+    findGears()
+    computePowers()
+    return gears.filter(g => g.neighbours == 2).map(g => g.ratio).sum
+  }
+  def main(args: Array[String]): Unit = {
+    val solution: Int = solve("res/day3/input1.txt")
+    println(solution)
+  }
+}