feat: day 3 part 2

Author: fdlk

day03.sc

@@ -3,23 +3,41 @@ import common.loadPackets
 val input = loadPackets(List("day03.txt"))
   .map(_.split("").map(_.toInt))
 
-val frequencies = input.head.indices
-  .map(i =>
-    input.map(_.apply(i))
+def frequencies: List[Array[Int]] => IndexedSeq[Map[Int, Int]] =
+  rows => rows.head.indices.map(i =>
+    rows.map(_.apply(i))
       .groupBy(x => x)
       .view
       .mapValues(_.size)
       .toMap)
 
 def toInteger(bits: Seq[Int]): Int = bits
-    .reverse
-    .zipWithIndex
-    .map {
-      case (0, _) => 0
-      case (_, index) => Math.pow(2, index).toInt
-    }.sum
+  .reverse
+  .zipWithIndex
+  .map {
+    case (0, _) => 0
+    case (_, index) => Math.pow(2, index).toInt
+  }.sum
 
-val gammaRate = toInteger(frequencies.map(x => x.maxBy(_._2)._1))
-val epsilonRate = toInteger(frequencies.map(x => x.minBy(_._2)._1))
+val mostCommon = frequencies(input).map(x => x.maxBy(_._2)._1)
+val gammaRate = toInteger(mostCommon)
+val leastCommon = frequencies(input).map(x => x.minBy(_._2)._1)
+val epsilonRate = toInteger(leastCommon)
 
-val part1 = gammaRate * epsilonRate
+val part1 = gammaRate * epsilonRate
+
+val filterRows: (Int, List[Array[Int]], List[Array[Int]] => IndexedSeq[Int]) => Array[Int] = {
+  case (_, rows, _) if rows.size == 1 => rows.head
+  case (index, rows, bits) => filterRows(
+    index + 1,
+    rows.filter(row => row(index) == bits(rows)(index)),
+    bits
+  )
+}
+
+val oxygenGeneratorRating = toInteger(filterRows(0, input,
+  rows => frequencies(rows).map(x => if (x.getOrElse(0, 0) == x.getOrElse(1, 0)) 1 else x.maxBy(_._2)._1)))
+val co2Rating = toInteger(filterRows(0, input,
+  rows => frequencies(rows).map(x => if (x.getOrElse(0, 0) == x.getOrElse(1, 0)) 0 else x.minBy(_._2)._1)))
+
+val part2 = oxygenGeneratorRating * co2Rating