map

问题 So we get a new set of strings, and we have one as map Keys. And we want to do one way set_difference (note - not set_symmetric_difference). So currently I have such ugly code like: std::map<std::string, boost::shared_ptr<some_class> > _ds; std::set<std::string> compare_and_clean(std::set<std::string> &new_) { std::set<std::string> result; std::set<std::string> old; for (std::map<std::string, std::string>::iterator mi = _ds.begin(); mi != _ds.end(); ++mi) old.insert(mi->first); std::set

问题 We are storing a String key in a HashMap that is a concatenation of three String fields and a boolean field. Problem is duplicate keys can be created if the delimiter appears in the field value. So to get around this, based on advice in another post, I'm planning on creating a key class which will be used as the HashMap key: class TheKey { public final String k1; public final String k2; public final String k3; public final boolean k4; public TheKey(String k1, String k2, String k3, boolean k4)

问题 The map::erase() method has two overloads to remove a single item: void erase ( iterator position ); size_type erase ( const key_type& x ); I need to check which version is likely to be faster - my guess would be the first, because the second probably has to call map::find() to look up the iterator? Can anyone confirm? Thanks! 回答1: The first one is amortized constant complexity, the second is logarithmic. It is unlikely that the constant term would be large enough to make the first version

问题 assumend I have a (filled) list std::list<std::pair<int,otherobject>> myList; and want to find() the first element within this list, where int has a specific value - how can I do that? To explain it a bit further: I want to append these pairs to the list with an int that identifies otherobject but is not unique. The order where these int/otherobject pairs arrive has to be kept. When an int is found during access to elements of this list the first occurence of that int has to be given back

问题 I have 2 tables in hive having Order's and Order_Detail's (having 1:n relation and joined on order_id) which I am trying to load to a single table taking advantage of hive complex data type - map[struct]. Say ORDER has below data, Order_id total_amount customer 123 10.00 1 456 12.00 2 and ORDER_DETAILS have Order_id Order_Item_id Item_amount Item_type 123 1 5.00 A 123 2 5.00 B 456 1 6.00 A 456 2 3.00 B 456 3 3.00 C I would like to create single table ORDERS with all order columns and order

问题 Is it possible to map key to Multi Dimensional Array List. Some thing like following example.. Map<K,V> Where K is key for list of alphabet and V is a multi dimensional array list or normal array list that stores list of word. Some thing like a application that reads a dictionary file. I want to see an example. Example can be anything related to Map and Multi Dimensional Array-list. Or is there any other efficient way to implement collection? I have never used such implementations so if there

问题 This question already has answers here : HashMap and int as key (10 answers) Closed 6 years ago . I want to store a set of int / String values, but the int s are not necessarily incremental, meaning the data can be: <1, "first">, <3, "second">, <9, "third">. So I'm trying to create the c# equivalent of a Dictionary<int, string> but it just fails to compile, saying "Syntax error on token "int", Dimensions expected after this token" on the line: private Map<int, String> courses; Can anyone

问题 I've always been told vectors are fast, and in my years of programming experience, I've never seen anything to contract that. I decided to (prematurely optimize and) write a associative class that was a thin wrapper around a sequential container (namely ::std::vector and provided the same interface as ::std::map . Most of the code was really easy, and I got it working with little difficulty. However, in my tests of various sized POD types (4 to 64 bytes), and std::strings , with counts

问题 I want to apply a function to all elements in the list, but I want to actually change the elements (which are objects), not view results. I think this is the problem with using map() or list comprehensions. class Thing(object): pass # some collection of things my_things # they are all big... # produces SyntaxError: invalid syntax [i.size = "big" for i in my_things] # produces SyntaxError: lambda cannot contain assignment map(lambda i: i.size="big", [i for i in my_things]) # no error, but is

问题 I am confused with Python multiprocessing. I am trying to speed up a function which process strings from a database but I must have misunderstood how multiprocessing works because the function takes longer when given to a pool of workers than with “normal processing”. Here an example of what I am trying to achieve. from time import clock, time from multiprocessing import Pool, freeze_support from random import choice def foo(x): TupWerteMany = [] for i in range(0,len(x)): TupWerte = [] s =