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I'm looking for a C++ associative map container type which I can perform multiple key lookups on. The map needs to have constant time lookups, but I don't care if it's ordered or unordered. It just needs to be fast.
For example, I want to store a bunch of std::vector objects in a map with an int and a void* as the lookup keys. Both the int and the void* must match for my vector to be retrieved.
Does such a container exist already? Or am I going to have to roll my own? If so, how could I implement it? I've been trying to store a boost::unordered_map inside another boost::unordered_map, but I have not had any success with this method, yet. Maybe I will continue Pershing this method if there is no simpler way.
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Class MultiKeyMap<K,V> A Map implementation that uses multiple keys to map the value. This class is the most efficient way to uses multiple keys to map to a value.
You can't have an hash map with multiple keys, but you can have an object that takes multiple parameters as the key. Create an object called Index that takes an x and y value. Then have your HashMap<Index, Value> to get your result. :) You need to override hashCode and equals .
HashMap can be one of the best data structures for mapping multiple keys to the same value.
Constant look up requires a hash map. You can use a the boost::unordered_map (or tr1). The key would be the combined hash of the int and the void pointer.
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If you don't want to use boost, you can try map< int, map<void*, vector> >. The lookups are however O(log(map size)).
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