#include <shared_mutex>
#include <thread>
#include <vector>
#include <iostream>

std::vector<int> data;
std::shared_mutex mtx;

// 读线程函数
void reader(int id) {
    std::shared_lock<std::shared_mutex> lock(mtx);
    std::cout << "Reader " << id << " sees data size: " << data.size() << "\n";
}

// 写线程函数
void writer(int id) {
    std::unique_lock<std::shared_mutex> lock(mtx);
    data.push_back(id);
    std::cout << "Writer " << id << " added item\n";
}

int main() {
    std::vector<std::thread> threads;
    
    // 启动多个读线程和少量写线程
    for (int i = 0; i < 10; ++i) {
        threads.emplace_back(reader, i);
    }
    for (int i = 0; i < 2; ++i) {
        threads.emplace_back(writer, i + 100);
    }

    for (auto& t : threads) {
        t.join();
    }
}