#include <thread>
#include <mutex>
#include <iostream>

std::mutex mtx;  // 全局互斥锁
int shared_data = 0;

void unsafe_function() {
    mtx.lock();           // 加锁
    shared_data++;        // 安全访问共享数据
    std::cout << "Data: " << shared_data << std::endl;
    mtx.unlock();         // 解锁
}

void safe_function() {
    std::lock_guard<std::mutex> guard(mtx);  // 构造时自动 lock()
    shared_data++;
    std::cout << "Data: " << shared_data << std::endl;
    // 离开作用域时自动 unlock()
}

#include <iostream>
#include <thread>
#include <mutex>
#include <vector>

std::mutex mtx;
int counter = 0;

void increment(int n) {
    for (int i = 0; i < n; ++i) {
        std::lock_guard<std::mutex> guard(mtx);
        counter++;
    }
}

int main() {
    std::vector<std::thread> threads;
    const int num_threads = 10;
    const int inc_per_thread = 1000;

    for (int i = 0; i < num_threads; ++i) {
        threads.emplace_back(increment, inc_per_thread);
    }

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

    std::cout << "Final counter value: " << counter << std::endl;  // 应为 10000
    return 0;
}