How do I find elements with custom comparators with std::set in multithreaded code?

In C++, using `std::set` with custom comparators allows you to define a specific ordering for the elements stored in the set. When working in a multithreaded environment, it is essential to ensure that the set is accessed and modified safely across multiple threads. Below is a guide on how to achieve this along with an example.

Using custom comparators can be particularly useful when you need to store complex objects in a set and want to maintain order based on specific attributes. However, care must be taken when accessing or modifying the set in a concurrent context to avoid data races.

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

// Custom comparator for std::set
struct CustomComparator {
    bool operator()(const int &a, const int &b) const {
        return a < b; // Order by numerical value
    }
};

std::set mySet;
std::mutex setMutex;

void addElement(int value) {
    std::lock_guard<:mutex> lock(setMutex);
    mySet.insert(value);
}

void printSet() {
    std::lock_guard<:mutex> lock(setMutex);
    for (const auto &element : mySet) {
        std::cout << element << " ";
    }
    std::cout << std::endl;
}

int main() {
    std::thread t1(addElement, 5);
    std::thread t2(addElement, 3);
    std::thread t3(addElement, 8);

    t1.join();
    t2.join();
    t3.join();

    printSet();

    return 0;
}