使用stringstream作为字符串堆栈

#include <iostream>
#include <sstream>
#include <vector>

class StringStack {
public:
    void push(const std::string& str) {
        stack.push_back(str);
        ss << str; // 将字符串写入stringstream
    }

    std::string pop() {
        if (stack.empty()) {
            throw std::out_of_range("Stack is empty");
        }
        std::string top = stack.back();
        stack.pop_back();
        // 重新构建stringstream，移除顶部元素
        ss.str("");
        for (const auto& s : stack) {
            ss << s;
        }
        return top;
    }

    std::string peek() const {
        if (stack.empty()) {
            throw std::out_of_range("Stack is empty");
        }
        return stack.back();
    }

    bool empty() const {
        return stack.empty();
    }

private:
    std::vector<std::string> stack;
    mutable std::stringstream ss; // mutable 允许在const方法中修改
};

int main() {
    StringStack strStack;
    strStack.push("Hello");
    strStack.push(" ");
    strStack.push("World");

    std::cout << "Peek: " << strStack.peek() << std::endl;
    std::cout << "Pop: " << strStack.pop() << std::endl;
    std::cout << "Peek after pop: " << strStack.peek() << std::endl;

    return 0;
}