cpp如何让主线程等待，直到其他线程在周期内完成

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

void task(int id) {
    // 模拟线程执行任务
    std::this_thread::sleep_for(std::chrono::seconds(2));
    std::cout << "Thread " << id << " completed." << std::endl;
}

int main() {
    std::vector<std::thread> threads;
    int numThreads = 5;

    // 创建并启动线程
    for (int i = 0; i < numThreads; ++i) {
        threads.push_back(std::thread(task, i));
    }

    // 等待每个线程完成
    for (auto& thread : threads) {
        thread.join();
    }

    std::cout << "All threads completed. Continue with main thread." << std::endl;

    return 0;
}