241010 개미굴

private static class Node implements Comparable<Node> {
	private final String name;
	private final List<Node> children;

	public Node(String name) {
		this.name = name;
		this.children = new ArrayList<>();
	}

	@Override
	public int compareTo(Node other) {
		return this.name.compareTo(other.name);
	}
}

public static void main(String[] args) throws IOException {
	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	int numberOfEntries = Integer.parseInt(br.readLine());
	Node root = new Node("root");
	StringBuilder resultBuilder = new StringBuilder();

	for (int i = 0; i < numberOfEntries; i++) {
		StringTokenizer st = new StringTokenizer(br.readLine());
		int pathLength = Integer.parseInt(st.nextToken());
		String[] path = new String[pathLength];
		for (int j = 0; j < pathLength; j++) {
			path[j] = st.nextToken();
		}
		buildTree(root, path, 0);
	}

	generateOutput(root, 0, resultBuilder);
	System.out.print(resultBuilder);
}

private static void buildTree(Node currentNode, String[] path, int depth) {
	if (depth == path.length) {
		return;
	}

	String currentName = path[depth];
	Node childNode = findChild(currentNode.children, currentName);

	if (childNode == null) {
		childNode = new Node(currentName);
		currentNode.children.add(childNode);
	}

	buildTree(childNode, path, depth + 1);
}

private static Node findChild(List<Node> children, String name) {
	for (Node child : children) {
		if (child.name.equals(name)) {
			return child;
		}
	}
	return null;
}

private static void generateOutput(Node node, int depth, StringBuilder sb) {
	if (!node.name.equals("root")) {
		for (int i = 1; i < depth; i++) {
			sb.append("--");
		}
		sb.append(node.name).append("\n");
	}

	Collections.sort(node.children);
	for (Node child : node.children) {
		generateOutput(child, depth + 1, sb);
	}
}

출처:https://www.acmicpc.net/problem/14725