Day19v2.java

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class Day19v2 {

	public static String replace(String where, String what, String with, int pos) {
		return where.substring(0, pos) + with + where.substring(pos + what.length());
	}

	public static void main(String[] args) {
		List<String[]> transforms = FileIO.getFileLinesSplit(".\\InputDay19.txt", " => ");

		String medicine = "ORnPBPMgArCaCaCaSiThCaCaSiThCaCaPBSiRnFArRnFArCaCaSiThCaCaSiThCaCaCaCaCaCaSiRnFYFArSiRnMgArCaSiRnPTiTiBFYPBFArSiRnCaSiRnTiRnFArSiAlArPTiBPTiRnCaSiAlArCaPTiTiBPMgYFArPTiRnFArSiRnCaCaFArRnCaFArCaSiRnSiRnMgArFYCaSiRnMgArCaCaSiThPRnFArPBCaSiRnMgArCaCaSiThCaSiRnTiMgArFArSiThSiThCaCaSiRnMgArCaCaSiRnFArTiBPTiRnCaSiAlArCaPTiRnFArPBPBCaCaSiThCaPBSiThPRnFArSiThCaSiThCaSiThCaPTiBSiRnFYFArCaCaPRnFArPBCaCaPBSiRnTiRnFArCaPRnFArSiRnCaCaCaSiThCaRnCaFArYCaSiRnFArBCaCaCaSiThFArPBFArCaSiRnFArRnCaCaCaFArSiRnFArTiRnPMgArF";

		// part 1

		List<String> molecules = new ArrayList<>();

		for (String[] trans : transforms) {
			int pos = 0;
			while ((pos = medicine.indexOf(trans[0], pos)) >= 0) {
				molecules.add(replace(medicine, trans[0], trans[1], pos));
				pos += trans[0].length();
			}
		}

		long count = molecules.stream().distinct().count();

		System.out.println("Part 1: Total unique molecules = " + count);

		// part 2
		Collections.shuffle(transforms);
		int count2 = 0;
		int reshuffleCount = 0;
		String tmp = new String(medicine);
		while (!tmp.equals("e")) {
			String last = tmp;
			for (String[] trans : transforms) {
				if (tmp.contains(trans[1])) {
					tmp = replace(tmp, trans[1], trans[0], tmp.indexOf(trans[1]));
					// System.out.println(medicine);

					count2++;
				}
			}
			if (last.equals(tmp) && (!tmp.equals("e"))) {
				Collections.shuffle(transforms);
				tmp = new String(medicine);
				count2 = 0;
				reshuffleCount++;
			}
		}

		System.out.println("Part 2: Transforms taken = " + count2 + " Reshuffled " + reshuffleCount + " times.");

	}

}