题解 | 点击消除

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

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String str = in.nextLine();
        Stack<Character> stack = new Stack<>();
        for (char c : str.toCharArray()) {
            if (c == ' ') continue; // 忽略空格
            if (!stack.isEmpty() && stack.peek() == c) {
                stack.pop(); // 相邻相同则消除
            } else {
                stack.push(c);
            }
        }
        // 输出剩余字符
        StringBuilder sb = new StringBuilder();
        for (char c : stack) {
            sb.append(c);
        }
        System.out.println(sb.toString() .equals("") ? 0 : sb);
    }
}