Day 2: Unit test

src/main/kotlin/day2/Day2.kt

@@ -11,6 +11,16 @@ object Day2 {
 }
 
 data class Game(val id: Int, val hands: List<Hand>) {
+    fun isCompatibleWith(hand: Hand) =
+        hand.fitsIn(
+            hands.fold(Hand(0, 0, 0)) { currentMax: Hand, next: Hand ->
+                Hand(
+                    maxOf(currentMax.red, next.red),
+                    maxOf(currentMax.green, next.green),
+                    maxOf(currentMax.blue, next.blue)
+                )
+            })
+
     companion object {
 
         /**
@@ -30,6 +40,8 @@ data class Game(val id: Int, val hands: List) {
 }
 
 data class Hand(val red: Int, val green: Int, val blue: Int) {
+    fun fitsIn(other: Hand) = red >= other.red && green >= other.green && blue >= other.blue
+
     companion object {
 
         /**

src/test/kotlin/day2/Day2Test.kt

@@ -6,6 +6,10 @@ class Day2Test {
 
     @Test
     fun readGames() {
-        Day2.readGames()
+        val compatibleGames = Day2.readGames().filter { game ->
+            Hand(12, 13, 14).let(game::isCompatibleWith)
+        }
+
+        assert(compatibleGames.map(Game::id).joinToString(separator=",") == "1,2,5")
     }
 }