AdventOfCode7.java

public class AdventOfCode7
{
	static class Command
	{
		enum CommandType
		{
			and,
			or,
			rshift,
			lshift,
			not,
			set;

			static CommandType herp(String derp)
			{
				return CommandType.valueOf(derp.toLowerCase());
			}
		}

		CommandType type;
		String target;
		String left;
		String right;

		Command(CommandType type, String target, String left, String right)
		{
			this.type = type;
			this.target = target;
			this.left = left;
			this.right = right;
		}

		@Override
		public String toString()
		{
			return "Command<" + type + ", " + left + ", " + right + " -> " + target + ">";
		}
	}

	public static void main(String[] args)
	{
		Map<String, Integer> wireValues = new HashMap<>();
		Map<String, Command> wireCommands = new HashMap<>();
		BufferedReader reader = new BufferedReader(new InputStreamReader(getClass().getResourceAsStream("/deleteMe")));
		String line;
		while ((line = reader.readLine()) != null)
		{
			String[] tokens = line.split(" ");
			String target = tokens[tokens.length-1];
			Command command;
			switch(tokens.length)
			{
				case 3:
					command = new Command(CommandType.set, target, tokens[0], null);
					break;
				case 4:
					command = new Command(CommandType.not, target, tokens[1], null);
					break;
				default:
					CommandType type = CommandType.herp(tokens[1]);
					command = new Command(type, target, tokens[0], tokens[2]);
					break;
			}
			wireCommands.put(target, command);
		}
		wireValues.put("b", 16076); // Only change for Part 2

		Command start = wireCommands.get("a");
		int value = evaluate(start, wireCommands, wireValues);
		System.out.println("a: " + value);
	}

	int uShort = 0xFFFF;
	private int evaluate(Command current, final Map<String, Command> wireCommands, final Map<String, Integer> wireValues)
	{
		if (wireValues.containsKey(current.target))
			return wireValues.get(current.target);
		System.out.println("Evaluating " + current);
		int value;
		switch (current.type)
		{
			case set:
				value = evalLeft(current, wireCommands, wireValues);
				break;
			case not:
				value = ~evalLeft(current, wireCommands, wireValues) & uShort;
				break;
			case and:
				value = evalLeft(current, wireCommands, wireValues) & evalRight(current, wireCommands, wireValues);
				break;
			case or:
				value = evalLeft(current, wireCommands, wireValues) | evalRight(current, wireCommands, wireValues);
				break;
			case lshift:
				value = (evalLeft(current, wireCommands, wireValues) << evalRight(current, wireCommands, wireValues)) & uShort;
				break;
			case rshift:
				value = (evalLeft(current, wireCommands, wireValues) >>> evalRight(current, wireCommands, wireValues)) & uShort;
				break;
			default:
				throw new IllegalArgumentException("herp");
		}
		wireValues.put(current.target, value);
		System.out.println("Wire " + current.target + " value " + value);
		return value;
	}

	int evalLeft(Command current, final Map<String, Command> wireCommands, final Map<String, Integer> wireValues)
	{
		int value;
		try
		{
			value = parseInt(current.left) & uShort;
		}
		catch (NumberFormatException ex)
		{
			value = evaluate(wireCommands.get(current.left), wireCommands, wireValues);
		}
		return value;
	}

	int evalRight(Command current, final Map<String, Command> wireCommands, final Map<String, Integer> wireValues)
	{
		int value;
		try
		{
			value = parseInt(current.right) & uShort;
		}
		catch (NumberFormatException ex)
		{
			value = evaluate(wireCommands.get(current.right), wireCommands, wireValues);
		}
		return value;
	}
}