240520 에디터

public static void main(String[] args) throws IOException {
	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

	Node root = new Node('\0');
	Node cur = root;
	String initialText = br.readLine();
	for (int i = 0; i < initialText.length(); i++) {
		cur = cur.add(initialText.charAt(i));
	}

	int commandCount = Integer.parseInt(br.readLine());
	while (commandCount-- > 0) {
		String command = br.readLine();
		char cmdType = command.charAt(0);
		if (cmdType == 'L') {
			cur = cur.moveLeft();
		} else if (cmdType == 'D') {
			cur = cur.moveRight();
		} else if (cmdType == 'B') {
			cur = cur.del();
		} else if (cmdType == 'P') {
			cur = cur.add(command.charAt(2));
		}
	}

	StringBuffer sb = new StringBuffer();
	for (cur = root.next; cur != null; cur = cur.next) {
		sb.append(cur.c);
	}
	System.out.println(sb.toString());
}

static class Node {
	private char c;
	private Node next;
	private Node prev;

	public Node(char c) {
		this.c = c;
		this.next = null;
		this.prev = null;
	}

	public Node add(char c) {
		Node newNode = new Node(c);
		if (this.next != null) {
			newNode.next = this.next;
			this.next.prev = newNode;
		}
		this.next = newNode;
		newNode.prev = this;
		return newNode;
	}

	public Node del() {
		if (this.prev == null) {
			return this;
		}
		if (this.next != null) {
			this.prev.next = this.next;
			this.next.prev = this.prev;
		} else {
			this.prev.next = null;
		}
		return this.prev;
	}

	public Node moveRight() {
		if (this.next != null) {
			return this.next;
		}
		return this;
	}

	public Node moveLeft() {
		if (this.prev != null) {
			return this.prev;
		}
		return this;
	}
}

출처:https://www.acmicpc.net/problem/1406