题解 | 点击消除

水题，直接用栈模拟即可，注意特判栈为空时，输出 0.

#include<bits/stdc++.h>
using i64 = long long;

int main() {
    std::cin.tie(nullptr)->sync_with_stdio(false);

    std::string s;
    std::cin >> s;
    std::vector<char> stk;

    for (auto c : s) {
        if (stk.size() && stk.back() == c) {
            stk.pop_back();
        } else {
            stk.push_back(c);
        }
    } 

    if (stk.empty()) {
        std::cout << 0;
    }

    for (auto c : stk) {
        std::cout << c;
    }

    return 0;
}

https://www.nowcoder.com/discuss/727521113110073344