Protect a shared container with a mutex.

#include <iostream>
#include <string>
#include <string_view>
#include <vector>
#include <array>
#include <algorithm>
#include <numeric>
#include <map>
#include <unordered_map>
#include <set>
#include <queue>
#include <stack>
#include <deque>
#include <tuple>
#include <bitset>
#include <memory>
#include <optional>
#include <variant>
#include <functional>
#include <charconv>
#include <regex>
#include <fstream>
#include <sstream>
#include <filesystem>
#include <iomanip>
#include <cmath>
#include <cctype>
#include <limits>
#include <chrono>
#include <thread>
#include <future>
#include <mutex>
#include <atomic>
#include <condition_variable>

int main() {
    std::cout << std::boolalpha;
    std::mutex mutex;
    std::vector<int> values;
    auto append=[&](int value){std::lock_guard<std::mutex> lock(mutex); values.push_back(value);};
    std::thread first(append,1),second(append,2);
    first.join(); second.join();
    std::sort(values.begin(),values.end());
    for (int value:values) std::cout << value << "\n";
}