set

问题 I was asking myself this question. Is Set a hashed collection in JavaScript? For example, Set.prototype.has will iterate the entire Set or do its implementations use an internal hash table to locate an item within the collection? 回答1: The ECMAScript 2015 specification says that: Set objects must be implemented using either hash tables or other mechanisms that, on average, provide access times that are sublinear on the number of elements in the collection. Obviously they can't force a

问题 This is a question for the algorithms gurus out there :-) Let S be a set of intervals of the natural numbers that might overlap and N be a list of numbers. I want to find the smallest subset (let's call P) of S such that for each number in our list N, there exists at least one interval in P that contains it. The intervals in P are allowed to overlap. Trivial example: S = {[1..4], [2..7], [3..5], [8..15], [9..13]} N = [1, 4, 5] // so P = {[1..4], [2..7]} I think a dynamic algorithm might not

问题 What is the algorithmic runtime of Python 2.7's isDisjoint(other) method for sets? Is it faster than simply doing intersection(other) and then checking len()>0 of that returned intersection? 回答1: The complexity in both cases is going to be O(min(len(s), len(t)) . The only difference is that intersection creates a new set of all matched items and isdisjoint simply returns a boolean and can short-circuit as soon as a match is found. Example that short-circuits right away: >>> s1 = set(range(10*

问题 Drawing a blank on this, and google was not helpful. Want to make a function like this: function JakPaste() let tmp = :set paste? if tmp == "paste" set nopaste else set paste endif endfunction map <F2> :call JakPaste()<CR> However this does not work. I have isolated the broken line: function JakPaste() let tmp = set paste? endfunction map <F2> :call JakPaste()<CR> Pressing F2 results in this error: Error detected while processing function JakPaste: line 1: E121: Undefined variable: set E15:

问题 array1 = [1, 2, 3, 4, 5, 6, 7, 8, 9] array2 = [1, 2, 2, 2, 5, 6, 6, 6, 9] temp = set(array2) array1.remove(temp) Traceback (most recent call last): File "Sudoku V2.py", line 6, in <module> array1.remove(temp) ValueError: list.remove(x): x not in list 回答1: Try this: array1 = [1, 2, 3, 4, 5, 6, 7, 8, 9] array2 = [1, 2, 2, 2, 5, 6, 6, 6, 9] set(array1).difference(array2) => set([3, 4, 7, 8]) The above makes use of the difference() method of sets, which returns a new set with elements in the set

问题 Given a mapping dict mapping : { 'John': 'A', 'Mary': 'B', 'Tim' :'C' } I am then provided a dict spend : { 'John': 23, 'Mary': 1, } and a dict revenue : { 'A': 12, 'B': 2, 'C': 23 } then: for k, v in spend.items(): # do stuff Within this loop, I want to check if an entry in revenue does not have a corresponding entry in spend (based on our mapping). One such example is Tim (because 'C' is present in revenue , but 'Tim' is not present in spend ). An approach of looping again (within this for

问题 I know that JavaScript now has sets, but I wonder if there is something to realize the function of multiSet , or if there is some framework that has the functions of multiset which I really need a lot. Or I have to code it by myself to do the research of Red-Black Tree ? 回答1: There are no built-in multiset structure, but there are some libraries that have such: mnemonist → MultiSet TSTL → TreeMultiSet Feel free to add your favorite library in this question. 来源： https://stackoverflow.com

问题 The code I tried, but doesn't work: class A { public: struct cmpr_t { bool operator() (int k1, int k2) { return mp[k1] < mp[k2]; // doesn't compile } }; map<int, int> mp; // storing key->value set<int, cmpr_t> ss; // just keys, ordered by corresponding value in mp }; I just want a map and also a set , the map stores data (key, value), and the set only contains the keys, and I want the set ordered by keys' corresponding values. So how to define the set? UPDATE Compiler error: In member

问题 Are there already some javascript functions that do the same as the cakephp functions Set::combine and Set::classicExtract on client side in the browser? http://book.cakephp.org/2.0/en/core-utility-libraries/set.html So that I can bring this array: a = [ { 'User' : { 'id' : 2, 'group_id' : 1, 'name' : 'Alfred' } }, { 'User' : { 'id' : 12, 'group_id' : 2, 'name' : 'Albert' } } ] with a function like Set::combine(a, '{n}.User.id', '{n}.User.name') into the format a = { 2 : 'Alfred', 12 :

问题 The question explains it, but what is the time complexity of the set difference operation in Python? EX: A = set([...]) B = set([...]) print(A.difference(B)) # What is the time complexity of the difference function? My intuition tells me O(n) because we can iterate through set A and for each element, see if it's contained in set B in constant time (with a hash function). Am I right? (Here is the answer that I came across: https://wiki.python.org/moin/TimeComplexity) 回答1: looks that you're