Implement day 16, in groovy.

2017/README.md

@@ -14,6 +14,7 @@ The current plan, in no particular order:
 - [x] Clojure - [Day 03](./day-03/solution.clj)
 - [ ] Coffeescript
 - [x] Go - [Day 13](./day-13/solution.go)
+- [x] Groovy - [Day 16](./day-16/solution.groovy)
 - [x] Haskell - [Day 15](./day-15/solution.hs)
 - [ ] Java
 - [x] Kotlin - [Day 10](./day-10/solution.kt)

2017/day-16/solution.groovy

@@ -0,0 +1,72 @@
+void doRotate(List<String> list, String arg) {
+	def amount = Integer.valueOf(arg.substring(1))
+
+	Collections.rotate(list, amount)
+}
+
+void exchangePos(List<String> list, String arg) {
+	def parts = arg.substring(1).split("/")
+
+	list.swap(Integer.valueOf(parts[0]), Integer.valueOf(parts[1]))
+}
+
+void exchangeProg(List<String> list, String arg) {
+	def p1 = list.indexOf(arg.substring(1, 2));
+	def p2 = list.indexOf(arg.substring(3, 4));
+
+	list.swap(p1, p2);
+}
+
+def input = System.in.newReader().readLine()
+
+def moves = input.split(",")
+
+def state = new LinkedList(Arrays.asList("abcdefghijklmnop".split("")))
+
+String dance(List<String> state, String[] moves) {
+	for (move in moves) {
+		switch (move.charAt(0)) {
+			case 's':
+				doRotate(state, move)
+					break;
+
+			case 'x':
+				exchangePos(state, move)
+					break;
+
+			case 'p':
+				exchangeProg(state, move)
+					break;
+
+			default:
+				println("Unknown type!")
+		}
+	}
+
+	return state.join("")
+}
+
+String danceOften(String[] moves, Integer amount) {
+	def state = new LinkedList(Arrays.asList("abcdefghijklmnop".split("")))
+
+	def seen = new HashSet<String>()
+	def order = new ArrayList<String>()
+
+	def summary = state.join("");
+
+	for (i in 0..<amount) {
+		if (seen.contains(summary)) {
+			return order.get(amount % i)
+		}
+
+		seen.add(summary)
+		order.add(summary)
+		summary = dance(state, moves)
+	}
+
+	return summary;
+}
+
+
+println dance(state, moves)
+println danceOften(moves, 1000000000)