multiset

Perhaps this is a duplicate but I did not find anything searching: When erase(value) is called on std::multiset all elements with the value found are deleted. The only solution I could think of is: std::multiset<int>::iterator hit(mySet.find(5)); if (hit!= mySet.end()) mySet.erase(hit); This is ok but I thought there might be better. Any Ideas ? user2251346 auto itr = my_multiset.find(value); if(itr!=my_multiset.end()){ my_multiset.erase(itr); } I would imagine there is a cleaner way of accomplishing the same. But this gets the job done. Try this one: multiset<int> s; s.erase(s.lower_bound

Given arrays (say row vectors) A and B, how do I find an array C such that merging B and C will give A? For example, given A = [2, 4, 6, 4, 3, 3, 1, 5, 5, 5]; B = [2, 3, 5, 5]; then C = multiset_diff(A, B) % Should be [4, 6, 4, 3, 1, 5] (the order of the result does not matter here). For the same A, if B = [2, 4, 5] , then the result should be [6, 4, 3, 3, 1, 5, 5] . (Since there were two 4 s in A and one 4 in B, the result C should have 2 - 1 = 1 4 in it. Similarly for the other values.) PS: Note that setdiff would remove all instances of 2, 3, and 5, whereas here they need to be removed just

Apparently you could do either, but the former is more common. Why would you choose the latter and how does it work? I read this: http://www.drdobbs.com/cpp/stls-red-black-trees/184410531 ; which made me think that they did it. It says: insert_always is a status variable that tells rb_tree whether multiple instances of the same key value are allowed. This variable is set by the constructor and is used by the STL to distinguish between set and multiset and between map and multimap. set and map can only have one occurrence of a particular key, whereas multiset and multimap can have multiple

As the question states ... I don't get the point about multiset s / multimap s . So, what's the purpose? 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 have their key and the amount still available is the value accumulated sales data of a shop, every time a product is sold the product id get's added to the multiset thereby increasing the amount

I know I can test if set1 is a subset of set2 with: {'a','b','c'} <= {'a','b','c','d','e'} # True But the following is also True: {'a','a','b','c'} <= {'a','b','c','d','e'} # True How do I have it consider the number of times an element in the set occurs so that: {'a','b','c'} <= {'a','b','c','d','e'} # True {'a','a','b','c'} <= {'a','b','c','d','e'} # False since 'a' is in set1 twice but set2 only once {'a','a','b','c'} <= {'a','a','b','c','d','e'} # True because both sets have two 'a' elements I know I could do something like: A, B, C = ['a','a','b','c'], ['a','b','c','d','e'], ['a','a','b',

I am porting some C++ code to Python and one of the data structures is a multiset, but I am not sure how to model this in Python. Let ms be the C++ multiset<int> How ms is used (posting some examples) multiset<int>::iterator it = ms.find(x) ms.erase(it) ms.insert(x) ms.end() ms.lower_bound(x) ms.clear() TooTone There isn't. See Python's standard library - is there a module for balanced binary tree? for a general discussion of the equivalents of C++ tree containers ( map , set , multimap , multiset ) in Python. The closest I can think of is to use a dictionary mapping integers to counts (also