By default, use vector as the preferred sequential container in C++. This is equivalent to List\<T> in .NET languages.

vector<string> apples;  
apples.push_back("Granny Smith");  

Use map (not unordered_map) as the default associative container. Use set, multimap, and multiset for degenerate & multi cases.

map<string, string> apple_color;  
// ...  
apple_color["Granny Smith"] = "Green";  

When performance optimization is needed, consider using:

1. The array type when embedding is important, for example, as a class member.

2. Unordered associative containers such as [unordered_map]((../standard-library/unordered-map-class.md). These have lower per-element overhead and constant-time lookup, but they can be harder to use correctly and efficiently.

3. Sorted vector. For more information, see Algorithms.

Don’t use C-style arrays. For older APIs that need direct access to the data, use accessor methods such as f(vec.data(), vec.size()); instead.

For more information about containers, see C++ Standard Library Containers.

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