If you try to access an element in a std::map using a key that doesn't exist already in the map, it will insert a default-constructed value with that key. This will lead to unexpected behavior if you're not aware that the insertion has occurred.
<pre><code class="lang-cpp">std::map&lt;int, std::string&gt; cities;
myMap[0] = "Rome";

//inserts default-constructed value "" with key 1
std::string value = myMap[1]; 

//outputs empty string ""
std::cout &lt;&lt; value &lt;&lt; std::endl;
</code></pre>

If you try to access an element in a std::map using a key that doesn't exist already in the map, it will insert a default-constructed value with that key. This will lead to unexpected behavior if you're not aware that the insertion has occurred.

```cpp
std::map<int, std::string> cities;
myMap[0] = "Rome";

//inserts default-constructed value "" with key 1
std::string value = myMap[1]; 

//outputs empty string ""
std::cout << value << std::endl; 
```

Bugs with std::map

Subtle insertion bug with std::map

Just as the name says, we'll enjoy learning C++, one nugget at a time ☕
