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C++20 STL Cookbook

Efficiently Insert Elements into a Map

Understand how to efficiently insert key-value pairs into C++ STL map containers. Explore differences between emplace and try_emplace methods to avoid unnecessary object construction, improving runtime performance especially with large payloads. Learn to implement and test these methods in practical C++20 code.

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The map class is an associative containerAn associative container is a type of data structure that enables efficient retrieval of values based on a unique key or identifier, without requiring traversal through other elements. that holds key/value pairs, where keys must be unique within the container.

There are a number of ways to populate a map container. Consider a map defined like this: 

map<string, string> m;

We can add an element with the [] operator: 

m["Miles"] = "Trumpet"

We can use the insert() member function: 

m.insert(pair<string,string>("Hendrix", "Guitar"));

Or, we can use the emplace() member function:

 m.emplace("Krupa", "Drums");

Many programmers tend to gravitate toward the emplace() function. Introduced with C++11, emplace() uses perfect forwarding to emplace (create in place) the new element for the container. The parameters are forwarded directly to the ...