day 5

src/main/scala/de.qwertyuiop.aoc/2021/day5.scala

@@ -2,5 +2,44 @@ package de.qwertyuiop.aoc.`2021`
 
 import de.qwertyuiop.aoc.lib.*
 import cats.*, cats.implicits.given
+import Vectors.{*,given}
+import util.chaining.given
+
+extension (a: Int)
+  def <->(b: Int): Range.Inclusive = (a min b) to (a max b)
+
+case class Line(start: Vec2D[Int], end: Vec2D[Int]):
+  def contains(p: Vec2D[Int]): Boolean =
+    (start.x == end.x && start.x == p.x && (start.y <-> end.y).contains(p.y))
+    ||
+    (start.y == end.y && start.y == p.y && (start.x <-> end.x).contains(p.x))
+    ||
+    (start.x + start.y == end.x + end.y && p.x + p.y == end.x + end.y
+      && (start.y <-> end.y).contains(p.y) && (start.x <-> end.x).contains(p.x))
+    ||
+    (p.x - p.y == end.x - end.y
+      && (start.y <-> end.y).contains(p.y) && (start.x <-> end.x).contains(p.x))
+
+def day5(using InputSource): Unit =
+  val lines = input{ case s"$x1,$y1 -> $x2,$y2" => Line(Vec2D(x1.toInt,y1.toInt), Vec2D(x2.toInt,y2.toInt))}
+  val orthogonalLines = lines.filter(l => l.start.x == l.end.x || l.start.y == l.end.y)
+  val maxX = lines.flatMap(l => List(l.start.x, l.end.x)).max
+  val maxY = lines.flatMap(l => List(l.start.y, l.end.y)).max
+  println(dangerPoints(orthogonalLines, maxX, maxY))
+  println(dangerPoints(lines, maxX, maxY))
+
+
+def dangerPoints(lines: List[Line], maxX: Int, maxY: Int) = (
+  for
+    x <- 0 to maxX
+    y <- 0 to maxY
+  yield lines.count(_.contains(Vec2D(x,y)))
+).count(_ > 1)
+
+//debug output like in the description for part1
+def printLines(lines: List[Line], maxX: Int, maxY: Int): Unit =
+  for y <- 0 to maxY do
+    for x <- 0 to maxX do
+      print(lines.count(_.contains(Vec2D(x, y))).pipe(i => if i > 0 then i.toString else "."))
+    println()
 
-def day5(using InputSource): Unit = ???