Unordered Map
概念
An unordered_map is a data structure that stores key-value pairs. It is a hash table that uses a hashing algorithm to map keys to values. Unlike a regular hash table, unordered_map does not store keys in the order they were inserted, making them more suitable for use cases where the order of keys does not matter.
分类
There are two main types of unordered_maps:
- Generic unordered_map: This is a generic version of the unordered_map that does not specify the key or value type. It is suitable for use cases where the key and value types are not known at compile time.
- Specific unordered_map: This is a version of the unordered_map that specifies the key and value types. It is suitable for use cases where the key and value types are known at compile time.
优势
Unordered maps offer several advantages over regular maps:
- Speed: Unordered maps are typically faster than regular maps because they do not require the overhead of maintaining a sorted order for the keys.
- No memory allocation: Unordered maps do not require memory allocation when inserting or retrieving items. This can save time and resources in certain scenarios.
- Random access: Unordered maps provide efficient random access to their elements, making them suitable for use cases where the order of keys does not matter.
应用场景
Unordered maps are commonly used in situations where speed and memory efficiency are critical, such as in game development, image processing, and data analysis. They are also used in algorithms that require fast lookups, such as in hash tables and hash maps.
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