The std::map is a fundamental part of the C++ Standard Template Library (STL), providing a sorted associative container that maintains key-value pairs with unique keys. The keys in a map are sorted using a comparison function, which allows efficient searching, insertion, and deletion operations—typically with logarithmic complexity.

Key Characteristics and Operations

• Sorted: The elements in a std::map are always sorted by key, which allows for efficient range queries.

• Unique Keys: Each element's key is unique within the map, ensuring that no two elements have the same key.

• Bidirectional Iterators: std::map provides iterators that allow traversal of the container in both directions.

• Allocator-aware: The container uses an allocator for dynamic memory management, which can be customized.

Basic Member Functions

• Construction and Destruction: A std::map can be constructed with a custom comparison function and allocator. It is destroyed when it goes out of scope or is explicitly deleted.

• Assignment: The operator= allows copying or moving a map's contents.

• Access: The at and operator[] functions provide access to elements by key, with operator[] also allowing insertion of new elements.

• Iterators: Functions like begin, end, rbegin, and rend return iterators to the start and end of the map, as well as in reverse order.

• Capacity: Functions such as empty, size, and max_size provide information about the map's storage.

• Modifiers: Functions like insert, erase, clear, and swap modify the map's contents.

• Observers: The key_comp and value_comp functions return the comparison objects used for keys and values.

• Operations: Functions like find, count, lower_bound, upper_bound, and equal_range perform various operations to search and manipulate the map.

• Allocator: The get_allocator function returns the map's allocator.