Add solution for day 2

src/Day02.kt

@@ -0,0 +1,72 @@
+fun main() {
+    fun part1(input: List<String>): Int {
+        val maxCubes = mapOf(
+            "red" to 12,
+            "green" to 13,
+            "blue" to 14
+        )
+        return input.map { Game.parse(it) }
+            .sumOf { game ->
+                val validGame = game.subsets.all { subset ->
+                    subset.none { (color, count) ->
+                        (count > maxCubes[color]!!)
+                    }
+                }
+                if (validGame) {
+                    game.id
+                } else {
+                    0
+                }
+            }
+    }
+
+    fun part2(input: List<String>): Int {
+        return input.map { Game.parse(it) }
+            .sumOf { game ->
+                val minNecessary = mutableMapOf(
+                    "blue" to 0,
+                    "green" to 0,
+                    "red" to 0
+                )
+                game.subsets.forEach { subset ->
+                    subset.forEach { (color, count) ->
+                        if (count > minNecessary[color]!!) {
+                            minNecessary[color] = count
+                        }
+                    }
+                }
+                var power = 1
+                minNecessary.values.forEach { power *= it }
+                power
+            }
+    }
+
+    // test if implementation meets criteria from the description, like:
+    val testInput = readInput("Day02_test")
+    check(part1(testInput) == 8)
+    check(part2(testInput) == 2286)
+
+    val input = readInput("Day02")
+    part1(input).println()
+    part2(input).println()
+}
+
+data class Game(val id: Int, val subsets: Set<Map<String, Int>>) {
+    companion object {
+        fun parse(s: String): Game {
+            val colonPosition = s.indexOf(':')
+            val id = s.substring(5, colonPosition).toInt()
+            val subsets = s.substring(colonPosition + 2)
+                .split(';')
+                .map { set ->
+                    set.split(',')
+                        .associate {
+                            val parts = it.trim().split(' ')
+                            parts[1] to parts[0].toInt()
+                        }
+                }
+                .toSet()
+            return Game(id, subsets)
+        }
+    }
+}