How do I erase elements while iterating with std::unordered_map for large datasets?

When working with large datasets in C++ and using `std::unordered_map`, it's essential to handle element removal correctly while iterating. Directly modifying the container while iterating can invalidate iterators and lead to undefined behavior. Here’s how you can safely erase elements in an `std::unordered_map`.

#include <iostream>
#include <unordered_map>

int main() {
    std::unordered_map<int, std::string> myMap = {
        {1, "one"},
        {2, "two"},
        {3, "three"},
        {4, "four"},
        {5, "five"}
    };

    for (auto it = myMap.begin(); it != myMap.end(); ) {
        if (it->first % 2 == 0) { // Remove even keys
            it = myMap.erase(it); // erase returns the next iterator
        } else {
            ++it; // Increment only if not erased
        }
    }

    // Print remaining elements
    for (const auto& pair : myMap) {
        std::cout << pair.first << ": " << pair.second << std::endl;
    }

    return 0;
}