Google Collections (now Guava) is a Java 1.5 library… even ignoring the lack of generics in Java 1.4, it likely uses things that were added in 1.5, making it incompatible. That said, there are various ways to iterate through a Multimap. By key, collection pairs in Java8: multimap.asMap().forEach((key, collection) -> {…}); Iterate through all values: … Read more
The C++ standard does not define how the standard containers should be implemented, it only gives certain constraints like the one you say for vectors. multimaps have certain runtime complexity (O(lg n) for the interesting operations) and other guarantees, and can be implemented as red-black trees. This is how they are implemented in the GNU … Read more
You can use std::multimap<char, int>::equal_range, which will give you an iterator range containing all pairs which have a certain key. So if you look for ‘b’, you will get an iterator range containing all pairs which have ‘b’ as the key. You can then simply iterate over the range, and erase any pair you see … Read more
pair<Iter, Iter> range = my_multimap.equal_range(“Group1”); int total = accumulate(range.first, range.second, 0); Is one way. Edit: If you don’t know the group you are looking for, and are just going through each group, getting the next group’s range can be done like so: template <typename Pair> struct Less : public std::binary_function<Pair, Pair, bool> { bool operator()(const … Read more
Some use cases: multimap With ZIP code as a key, all people which have that ZIP code With account ID as key, all open orders of that person/account A dictionary, with per keyword various explanations multiset is in essence a map with a key and a integer count. The inventory of a shop, all products … Read more
It’s hard to tell whether your benchmark is doing the right thing, so I can’t comment on the numbers. However, a few general points: Why multimap rather than map of vectors: Maps, multimaps, sets and multisets are all essentially the same data structure, and once you have one, it’s trivial to just spell out all … Read more
You can use upper_bound to increment the iterator position instead of ++: #include <map> #include <string> #include <iostream> using namespace std; int main() { multimap<int,string> mm; mm.insert(make_pair(1, “a”)); mm.insert(make_pair(1, “lemon”)); mm.insert(make_pair(2, “peacock”)); mm.insert(make_pair(3, “angel”)); for( auto it = mm.begin(), end = mm.end(); it != end; it = mm.upper_bound(it->first) ) cout << it->first << ‘ ‘ … Read more
Assuming you have Map<String, Collection<String>> map = …; Multimap<String, String> multimap = ArrayListMultimap.create(); Then I believe this is the best you can do for (String key : map.keySet()) { multimap.putAll(key, map.get(key)); } or the more optimal, but harder to read for (Entry<String, Collection<String>> entry : map.entrySet()) { multimap.putAll(entry.getKey(), entry.getValue()); }
Because it’s almost christmas 🙂 ////////////////////////////////////////////////////////////////////// // Algorithmia is (c) 2008 Solutions Design. All rights reserved. // http://www.sd.nl ////////////////////////////////////////////////////////////////////// // COPYRIGHTS: // Copyright (c) 2008 Solutions Design. All rights reserved. // // The Algorithmia library sourcecode and its accompanying tools, tests and support code // are released under the following license: (BSD2) // ———————————————————————- // … Read more
Why not wrap ConcurrentHashMap[T,ConcurrentLinkedQueue[U]] with some nice Scala-like methods (e.g. implicit conversion to Iterable or whatever it is that you need, and an update method)?