I have a question with hash_map and map in C++. I understand that map is in STL, but hash_map is not a standard. What’s the difference between the two?
I have a question with hash_map and map in C++. I understand that map
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I have a question with hash_map and map in C++. I understand that map is in STL, but hash_map is not a standard. What’s the difference between the two?
They are implemented in very different ways.
hash_map(unordered_mapin TR1 and Boost; use those instead) use a hash table where the key is hashed to a slot in the table and the value is stored in a list tied to that key.mapis implemented as a balanced binary search tree (usually a red/black tree).An
unordered_mapshould give slightly better performance for accessing known elements of the collection, but amapwill have additional useful characteristics (e.g. it is stored in sorted order, which allows traversal from start to finish).unordered_mapwill be faster on insert and delete than amap.