Advent of Code 2022: Day 13

class PDU implements Comparable<PDU> { private final List<PDU> child = new ArrayList<>(); private int val = -1; private boolean isNum = true; private final String rawValue; public PDU(String input) { this.rawValue = input; if (!input.startsWith("[")) { val = Integer.parseInt(input); } else { input = input.substring(1, input.length() - 1); int level = 0; StringBuilder tmp = new StringBuilder(); for (char c : input.toCharArray()) { if (c == ',' && level == 0) { child.add(new PDU(tmp.toString())); tmp = new StringBuilder(); } else { level += (c == '[') ? 1 : (c == ']') ? -1 : 0; tmp.append(c); } } if (!tmp.toString().equals("")) { child.add(new PDU(tmp.toString())); } isNum = false; } } @Override public int compareTo(PDU other) { if (isNum && other.isNum) { return Integer.compare(other.val, val); } if (!isNum && !other.isNum) { for (int i = 0; i < Math.min(child.size(), other.child.size()); i++) { int val = child.get(i).compareTo(other.child.get(i)); if (val != 0) { return val; } } return other.child.size() - child.size(); } PDU pdu1 = isNum ? new PDU("[" + val + "]") : this; PDU pdu2 = other.isNum ? new PDU("[" + other.val + "]") : other; return pdu1.compareTo(pdu2); } @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; PDU that = (PDU) o; return rawValue.equals(that.rawValue); } @Override public int hashCode() { return Objects.hashCode(rawValue); } } static void day13(String puzzleInputUri) throws IOException, InterruptedException { String[] packets = client.send(request.uri((URI.create(puzzleInputUri))).build(), HttpResponse.BodyHandlers.ofLines()) .body() .filter(line -> line.startsWith("[")) .toArray(String[]::new); int answerPartOne = 0; List<PDU> broadcast = new ArrayList<>(); for (int i = 0, pairIdx = 1; i < packets.length - 1; i += 2, pairIdx++) { PDU left = new PDU(packets[i]); PDU right = new PDU(packets[i+1]); broadcast.addAll(List.of(left, right)); answerPartOne += left.compareTo(right) > 0 ? pairIdx : 0; } System.out.println(answerPartOne); PDU separator1 = new PDU("[[2]]"); PDU separator2 = new PDU("[[6]]"); broadcast.addAll(List.of(separator1, separator2)); broadcast.sort(Comparator.reverseOrder()); int answerPartTwo = (broadcast.indexOf(separator1) + 1) * (broadcast.indexOf(separator2) + 1); System.out.println(answerPartTwo); }