Day 13 part 2

benoitpas · Dec 15, 2023 · 8335b8c · 8335b8c
1 parent 2827dc7
commit 8335b8c
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Showing 2 changed files with 25 additions and 18 deletions.
diff --git a/src/main/scala/day13.scala b/src/main/scala/day13.scala
@@ -12,47 +12,50 @@ object Day13 extends ZIOAppDefault {
       }
       ._1
 
-  def findVerticalReflection(pattern: Array[Array[Char]]): Option[Int] =
+  def findVerticalReflection(pattern: Array[Array[Char]], nbDiff: Int) =
     val nbCol = pattern(0).length
     val nbRow = pattern.length
     (1 to nbCol - 1)
       .to(LazyList)
       .map { i =>
         val n = math.min(i, nbCol - i)
         // compare colomns
-        val eq = (1 to n).foldLeft(true) { case (a, j) =>
-          (0 to nbRow - 1).foldLeft(a) { (a, k) => a && pattern(k)(i - j) == pattern(k)(i + j - 1) }
+        val eq = (1 to n).foldLeft(0) { case (a, j) =>
+          (0 to nbRow - 1).foldLeft(a) { (a, k) => a + (if pattern(k)(i - j) == pattern(k)(i + j - 1) then 0 else 1) }
         }
-        (eq, i)
+        (eq == nbDiff, i)
       }
       .find(_._1)
       .map(_._2)
 
-  def findHorizontalReflection(pattern: Array[Array[Char]]) =
+  def findHorizontalReflection(pattern: Array[Array[Char]], nbDiff: Int) =
+    val nbCol = pattern(0).length
     val nbRow = pattern.length
     (1 to nbRow - 1)
       .to(LazyList)
       .map { i =>
         val n = math.min(i, nbRow - i)
         // compare rows
-        val eq = (1 to n).foldLeft(true) { case (a, j) =>
-          a && (pattern(i - j) sameElements pattern(i + j - 1))
+        val eq = (1 to n).foldLeft(0) { case (a, j) =>
+          (0 to nbCol - 1).foldLeft(a) { (a, k) => a + (if pattern(i - j)(k) == pattern(i + j - 1)(k) then 0 else 1) }
+//          a + ( if (pattern(i - j) sameElements pattern(i + j - 1)) then 0 else 1)
         }
-        (eq, i)
+        (eq == nbDiff, i)
       }
       .find(_._1)
       .map(_._2)
 
-  def findReflection(pattern: Array[Array[Char]]) =
-    findHorizontalReflection(pattern).getOrElse(0) * 100 + findVerticalReflection(pattern).getOrElse(0)
+  def findReflection(nbDiff: Int)(pattern: Array[Array[Char]]) =
+    findHorizontalReflection(pattern, nbDiff).getOrElse(0) * 100 + findVerticalReflection(pattern, nbDiff).getOrElse(0)
 
-  def part1(strings: List[String]) =
+  def part12(strings: List[String], nbDiff: Int) =
     val patterns = parseValley(strings)
-    patterns.map(findReflection).sum
+    patterns.map(findReflection(nbDiff)).sum
 
   def run =
     for {
       v <- Day1.readFile("day13_input.txt")
-      _ <- printLine(s"part1=${part1(v)}")
+      _ <- printLine(s"part1=${part12(v, 0)}")
+      _ <- printLine(s"part2=${part12(v, 1)}")
     } yield ()
 }
diff --git a/src/test/scala/day13_test.scala b/src/test/scala/day13_test.scala
@@ -30,15 +30,19 @@ class Day13Test {
   val patterns = Day13.parseValley(valley)
 
   @Test
-  def testFindHorizontalReflection() =
-    assertEquals(Some(4), Day13.findHorizontalReflection(patterns(1)))
+  def testFindHorizontalReflection1() =
+    assertEquals(Some(4), Day13.findHorizontalReflection(patterns(1), 0))
 
   @Test
-  def testFindReflection() =
-    assertEquals(3, Day13.findReflection(pattern))
+  def testFindReflection1() =
+    assertEquals(3, Day13.findReflection(0)(pattern))
 
   @Test
   def testPart1() =
-    assertEquals(405, Day13.part1(valley))
+    assertEquals(405, Day13.part12(valley, 0))
+
+  @Test
+  def testPart2() =
+    assertEquals(400, Day13.part12(valley, 1))
 
 }