stdset

I have a std::set<int> , what's the proper way to find the largest int in this set? What comparator are you using? For the default this will work: if(!myset.empty()) *myset.rbegin(); else //the set is empty This will also be constant time instead of linear like the max_element solution. Sets are always ordered. Assuming you are using the default comparison (less), just grab the last element in the set. rbegin() might be useful. I believe you are looking for std::max_element : The max_element() function returns an iterator to the largest element in the range [start,end). Since set sorts the

This may be a stupid question, I am quite new to C++ and programming in general. I wish to understand the use of several STL containers and with that in mind, I was wondering what the advantages are of using std::set vs for example using vectors or maps? I can't seem to find an explicit answer to this question. I noticed that sets use maps, but then why not always use maps or always use sets. Instead 2 quite similar containers are provided. Thanks in advance. Both std::set and std::map are associative containers. The difference is that std::set s contain only the key, while in std::map there

I'm heavily using std::set<int> and often I simply need to check if such a set contains a number or not. I'd find it natural to write: if (myset.contains(number)) ... But because of the lack of a contains member, I need to write the cumbersome: if (myset.find(number) != myset.end()) .. or the not as obvious: if (myset.count(element) > 0) .. Is there a reason for this design decision ? I think it was probably because they were trying to make std::set and std::multiset as similar as possible. (And obviously count has a perfectly sensible meaning for std::multiset .) Personally I think this was a

In C++, I have a std::set that I would like to insert a range of consecutive integers. How can I do this efficiently, hopefully in O(n) time where n is the length of the range? I'm thinking I'd use the inputIterator version of std::insert, but am unclear on how to build the input iterator. std::set<int> mySet; // Insert [34 - 75): mySet.insert(inputIteratorTo34, inputIteratorTo75); How can I create the input iterator and will this be O(n) on the range size? The efficient way of inserting already ordered elements into a set is to hint the library as to where the next element will be. For that

Let's say I have the following: struct MetadataThingy { void *actual_thingy; int some_metadata; int more_metadata; bool operator<(MetadataThingy const& other) const { return actual_thingy < other.actual_thingy; } }; where actual_thingy points to some data of importance and I want the container ordered by the value of actual_thingy rather than the value of the element pointed at, but I need to store some other data about it, so I created the wrapper class MetadataThingy with a comparator that only considers the value of the actual_thingy pointer (rather than using a container of void * ) Now,