I need to create a hash table that has a key as a string, and value as an int. I cannot use STL containers on my target. Is there a suitable hash table class for this purpose?
A:
You can use the unordered associative container from Boost, aka. boost::unordered_map, which is implemented in terms of a hash table.
Konrad Rudolph
2010-05-19 15:23:43
although it would be interesting what the poster's opposition to STL is. If it is the fact that templates are used then boost is out as well.
mjmarsh
2010-05-19 15:25:22
@mjmarsh: True but in that case a lot more information would have been helpful. Even excluding the STL is an unreasonable request as far as I am concerned but since no other restrictions were mentioned, I think using the Boost libraries are probably the obvious choice.
Konrad Rudolph
2010-05-19 15:28:24
A:
It's a moot point since STL has no hash table container; std::map would be the alternative. For most purposes there is no reason not to use std::map. For uses that require a hashtable, boost::unordered_map is the best choice (and I think matches the hashtable defined in the new C++ TR1 proposed standard. Some compilers -- but I can't name them -- may provide the TR1 hashtable as std::tr1::unordered_map
c-urchin
2010-05-19 15:47:05
A:
You might want to check out glib hash tables
http://library.gnome.org/devel/glib/stable/glib-Hash-Tables.html
frankc
2010-05-19 15:49:40
+1
A:
In the case that you know your list of keys ahead of time (or some superset thereof), you can use a perfect hash function generator like gperf. gperf will spit out either C or C++ code.
(You may need to do some work to actually build a container, given the hash function, though.)
leander
2010-05-19 15:55:28
A:
If you need maximum performance, use MCT's closed_hash_map or Google's dense_hash_map. The former is easier to use, the latter is more mature. Your use case sounds like it would benefit from closed hashing.
doublep
2010-05-19 19:00:02