题解 | #点击消除#

import java.util.Stack;
import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        // while (in.hasNextInt()) { // 注意 while 处理多个 case
        //     int a = in.nextInt();
        //     int b = in.nextInt();
        //     System.out.println(a + b);
        // }
        String line = in.nextLine();
        String result = "";
        Stack<Character> stack = new Stack<>(); 
        for (int i = 0; i < line.length(); i++) {
            if (!stack.isEmpty() && stack.peek() == line.charAt(i)) {
                stack.pop();
            } else if (stack.isEmpty() || stack.peek() != line.charAt(i)) {
                stack.push(line.charAt(i));
            }
        }
        if (stack.isEmpty()) {
            System.out.println(0);
        } else {
            while (!stack.isEmpty()) {
                result = stack.pop() + result;
            }
            System.out.println(result.toString());
        }
    }
}