From 09911c195c0a2272fe114fd9cf1f20e47af6f6d6 Mon Sep 17 00:00:00 2001
From: Xavier Morel <morelx42@gmail.com>
Date: Fri, 7 Dec 2018 15:00:59 +0100
Subject: [PATCH] Adding day 7

---
 day7/part1.scala | 30 ++++++++++++++++++++++++++++
 day7/part2.scala | 51 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 81 insertions(+)
 create mode 100644 day7/part1.scala
 create mode 100644 day7/part2.scala

diff --git a/day7/part1.scala b/day7/part1.scala
new file mode 100644
index 0000000..252abd4
--- /dev/null
+++ b/day7/part1.scala
@@ -0,0 +1,30 @@
+import scala.io.StdIn.readLine
+
+// "Step A must be finished before step B can begin."
+//  0    1 2    3  4        5      6    7 8   9
+val PREREQ_STEP_INDEX: Int = 1
+val STEP_INDEX: Int = 7
+
+val stepsWithParents = Iterator.continually(readLine)
+  .takeWhile(_ != null)
+  .map { l =>
+    val ws = l.split(" ")
+    ws(PREREQ_STEP_INDEX).head -> ws(STEP_INDEX).head }
+  .foldLeft(Map.empty[Char, Set[Char]]){
+    case (acc, (parent, child)) => acc +
+      (child -> (acc.getOrElse(child, Set.empty[Char]) + parent)) +
+      (parent -> (acc.getOrElse(parent, Set.empty[Char])))}
+  .toList
+
+def walkGraph(g: List[(Char, Set[Char])], result: String = ""): String = g match {
+  case Nil => result
+  case _ => 
+    val chosenParent = g.filter(_._2.isEmpty).map(_._1).min
+    walkGraph(
+      g
+        .filter(_._1 != chosenParent)
+        .map { case (k, v) => k -> v.filter(_ != chosenParent) },
+      result + chosenParent.toString)
+}
+
+println(walkGraph(stepsWithParents))
diff --git a/day7/part2.scala b/day7/part2.scala
new file mode 100644
index 0000000..420645d
--- /dev/null
+++ b/day7/part2.scala
@@ -0,0 +1,51 @@
+import scala.io.StdIn.readLine
+
+// "Step A must be finished before step B can begin."
+//  0    1 2    3  4        5      6    7 8   9
+val PREREQ_STEP_INDEX: Int = 1
+val STEP_INDEX: Int = 7
+
+val BASE_TIME_TO_COMPLETE: Int = 61 // 60 + 1 because index of letter starting at 0.
+val WORKERS_NB: Int = 4
+
+val stepsWithParents = Iterator.continually(readLine)
+  .takeWhile(_ != null)
+  .map { l =>
+    val ws = l.split(" ")
+    ws(PREREQ_STEP_INDEX).head -> ws(STEP_INDEX).head }
+  .foldLeft(Map.empty[Char, Set[Char]]){
+    case (acc, (parent, child)) => acc +
+      (child -> (acc.getOrElse(child, Set.empty[Char]) + parent)) +
+      (parent -> (acc.getOrElse(parent, Set.empty[Char])))}
+  .toList
+
+def timeToComplete(c: Char): Int = BASE_TIME_TO_COMPLETE + (c - 'A')
+
+def updateResult(chosenParents: Seq[Char], children: Map[Char, Set[Char]], initial: Map[Char, Int]): Map[Char, Int] = {
+  val updatedParents = initial.map {
+    case (k, v) if chosenParents.contains(k) =>
+      k -> (v + timeToComplete(k))
+    case (k, v) => k -> v
+  }
+
+  updatedParents.map {
+    case (k, v) if children.contains(k) && children(k).exists(chosenParents.contains) =>
+      k -> (children(k).filter(chosenParents.contains).map(p => updatedParents(p)) + v).max
+    case (k, v) => k -> v
+  }
+}
+
+def walkGraph(g: List[(Char, Set[Char])], result: Map[Char, Int]): Map[Char, Int] =
+  g match {
+    case Nil => result
+    case _ =>
+      val chosenParents = g.filter(_._2.isEmpty).map(_._1).sorted.take(WORKERS_NB)
+      walkGraph(
+        g.filter(e => !chosenParents.contains(e._1))
+          .map { case (k, v) => k -> v.filterNot(chosenParents.contains) },
+        updateResult(chosenParents, g.toMap, result))
+}
+
+val timesToCompletion = walkGraph(stepsWithParents, stepsWithParents.map(_._1 -> 0).toMap)
+
+println(timesToCompletion('C'))