C++ Data StructuresLesson 54Free preview

C++ Maps

This lesson is part of C++ · All levels

Summary

Std::map stores key-value pairs sorted by key, so that each key is unique and can be searched quickly. The value is taken with the operator [] or at(), and a new key is automatically created when [] is used on an existing key. Maps are perfect for data named like dictionaries, ID-to-data indexes, or word count statistics.

Key points

The map std::pair<key, value> pairs and is sorted by key.
M[key] takes or creates entries; m.at(key) only takes and throws out_of_range when there is none.
M.find(k) returns the iterator, and m.end() marks the key is not found.
The iteration results in p.first (key) and p.second (value).

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