Day 25 initial commit

Author: mathiassteger

src/day25/Main.java

@@ -0,0 +1,202 @@
+package day25;
+
+import java.util.HashMap;
+
+public class Main {
+	static boolean[] tape = new boolean[1];
+	static HashMap<Integer, State> states = new HashMap<>(); // A = 0,.., F = 5
+	static State currentState;
+	static int steps = 12261543;
+	static int currentPos = 0;
+
+	public static void main(String[] args) {
+		states.put(0, new A());
+		states.put(1, new B());
+		states.put(2, new C());
+		states.put(3, new D());
+		states.put(4, new E());
+		states.put(5, new F());
+		
+		currentState = states.get(0);
+		
+		for (int i = 0; i < steps; i++) {
+			currentState = states.get(currentState.move());
+		}
+		
+		int counter = 0;
+		
+		for(boolean b : tape){
+			if(b)
+				counter++;
+		}
+		
+		System.out.println(counter);
+	}
+
+	static void goLeft() {
+		currentPos--;
+		if (currentPos < 0) {
+			boolean[] newTape = new boolean[tape.length + 1];
+			System.arraycopy(tape, 0, newTape, 1, tape.length);
+			tape = newTape;
+			currentPos++;
+		}
+	}
+
+	static void goRight() {
+		currentPos++;
+		if (currentPos > tape.length - 1) {
+			boolean[] newTape = new boolean[tape.length + 1];
+			System.arraycopy(tape, 0, newTape, 0, tape.length);
+			tape = newTape;
+		}
+	}
+}
+
+interface State {
+	int move();
+}
+
+class A implements State {
+
+	// If the current value is 0:
+	// - Write the value 1.
+	// - Move one slot to the right.
+	// - Continue with state B.
+	// If the current value is 1:
+	// - Write the value 0.
+	// - Move one slot to the left.
+	// - Continue with state C.
+
+	public int move() {
+		if (!Main.tape[Main.currentPos]) {
+			Main.tape[Main.currentPos] = true;
+			Main.goRight();
+			return 1;
+		} else {
+			Main.tape[Main.currentPos] = false;
+			Main.goLeft();
+			return 2;
+		}
+	}
+}
+
+class B implements State {
+
+	// If the current value is 0:
+	// - Write the value 1.
+	// - Move one slot to the left.
+	// - Continue with state A.
+	// If the current value is 1:
+	// - Write the value 1.
+	// - Move one slot to the right.
+	// - Continue with state C.
+
+	public int move() {
+		if (!Main.tape[Main.currentPos]) {
+			Main.tape[Main.currentPos] = true;
+			Main.goLeft();
+			return 0;
+		} else {
+			Main.tape[Main.currentPos] = true;
+			Main.goRight();
+			return 2;
+		}
+	}
+}
+
+class C implements State {
+
+	// If the current value is 0:
+	// - Write the value 1.
+	// - Move one slot to the right.
+	// - Continue with state A.
+	// If the current value is 1:
+	// - Write the value 0.
+	// - Move one slot to the left.
+	// - Continue with state D.
+
+	public int move() {
+		if (!Main.tape[Main.currentPos]) {
+			Main.tape[Main.currentPos] = true;
+			Main.goRight();
+			return 0;
+		} else {
+			Main.tape[Main.currentPos] = false;
+			Main.goLeft();
+			return 3;
+		}
+	}
+}
+
+class D implements State {
+
+	// If the current value is 0:
+	// - Write the value 1.
+	// - Move one slot to the left.
+	// - Continue with state E.
+	// If the current value is 1:
+	// - Write the value 1.
+	// - Move one slot to the left.
+	// - Continue with state C.
+
+	public int move() {
+		if (!Main.tape[Main.currentPos]) {
+			Main.tape[Main.currentPos] = true;
+			Main.goLeft();
+			return 4;
+		} else {
+			Main.tape[Main.currentPos] = true;
+			Main.goLeft();
+			return 2;
+		}
+	}
+}
+
+class E implements State {
+
+	// If the current value is 0:
+	// - Write the value 1.
+	// - Move one slot to the right.
+	// - Continue with state F.
+	// If the current value is 1:
+	// - Write the value 1.
+	// - Move one slot to the right.
+	// - Continue with state A.
+
+	public int move() {
+		if (!Main.tape[Main.currentPos]) {
+			Main.tape[Main.currentPos] = true;
+			Main.goRight();
+			return 5;
+		} else {
+			Main.tape[Main.currentPos] = true;
+			Main.goRight();
+			return 0;
+		}
+	}
+}
+
+class F implements State {
+
+	// If the current value is 0:
+	// - Write the value 1.
+	// - Move one slot to the right.
+	// - Continue with state A.
+	// If the current value is 1:
+	// - Write the value 1.
+	// - Move one slot to the right.
+	// - Continue with state E.
+
+	public int move() {
+		if (!Main.tape[Main.currentPos]) {
+			Main.tape[Main.currentPos] = true;
+			Main.goRight();
+			return 0;
+		} else {
+			Main.tape[Main.currentPos] = true;
+			Main.goRight();
+			return 4;
+		}
+	}
+}