How can I merge two maps in C++?

How can I merge two maps in C++?

You can merge two maps in C++ using the insert method or the operator+=. Would you like an example?

Yes, please provide an example using std::map.

Sure! Here's a simple example:

#include <iostream>
#include <map>

int main() {
    std::map<int, std::string> map1 = {{1, "One"}, {2, "Two"}};
    std::map<int, std::string> map2 = {{2, "Deux"}, {3, "Three"}};

    for (const auto& pair : map2) {
        map1.insert(pair);
    }

    for (const auto& pair : map1) {
        std::cout << pair.first << " : " << pair.second << std::endl;
    }
    return 0;
}

This will merge map2 into map1. Let me know if you need further clarification!

What happens if there are duplicate keys?

If there are duplicate keys, the values from the second map will not overwrite the values in the first map when using insert. If you want to overwrite, you can use the operator[] instead.

Can you show me how to overwrite values with duplicate keys?

Certainly! You can use the following code:

for (const auto& pair : map2) {
    map1[pair.first] = pair.second; // This will overwrite existing keys
}

This way, if a key exists in both maps, the value from map2 will replace the value in map1.