set

问题 Update : As Brian pointed out, my original idea did indeed have a concurrency issue. This was somewhat obscured by the signature of the ConcurrentDictionary<TKey, TValue>.AddOrUpdate method, which can lull a lazy thinker (like myself) into believing that everything--the set add as well as the queue push--will somehow happen all at once, atomically (i.e., magically). In retrospect, it was foolish of me to have this expectation. In fact, regardless of the implementation of AddOrUpdate , it

问题 Should I pass std::string by value or by reference to one function. This function store this values in member variable of class. I am always confuse when about pass by value or reference. Please clear my confusion about this. Here is code : class DataStore { public: void addFile(const string& filename, const set< std::string>& filePaths) { if (dataStoreMap.insert(make_pair(filename, filePaths)).second) { cout << "Data Added" <<endl; } else { cout << "Data not Added" << endl; } } private: //

问题 I can convert from NSMutableSet to Set no problem, but I'm running into problems when doing the reverse. E.g. this works: let nsSet = NSMutableSet(array: ["a", "b"]) let swiftSet = nsSet as! Set<String> But when I try: let nsSet2 = swiftSet as? NSMutableSet nsSet2 ends up being nil . 回答1: Looks like swift Sets need to be converted to NSSet first: let nsSet2 = NSMutableSet(set: set as NSSet) Or shorthand: let nsSet2 = NSMutableSet(set: set) Or to go from NSSet to Swift Set and back to NSSet:

问题 Say I have a set, like such: my_set = {"aaron", "cathy", "john", "stewie", "xavier"}; Say I want a function like such: FindFirst(my_set, "a") // returns an iterator pointing to "aaron" FindFirst(my_set, "aaron") // returns an iterator pointing to "aaron" FindFirst(my_set, "bill") // returns an iterator pointing to "cathy" FindFirst(my_set, "zzzzz") // returns past-the-end iterator Basically, it takes a value and returns an iterator either to that element, or the first element after it

问题 Is there a way to put some dict objects into a set in Python by using a simple method, like a comparator function? Came across a few solutions on here that involved a bunch of stuff that looked really complex and error-prone (seemed to be problems with iterating over the dict in undefined orders, etc...). Would be nice to do something like this which is technically not mathematically valid because two objects can have different information, but be evaluated as equal, but works great for

问题 I can easily declare a enumeration and a set. But sometimes I want to work with only part of the enumeration and I'd like the compiler to check for me if values in the sub-enum and its subset stay within the bounds. type TDay = (mon, tue, wen, thu, fri, sat, sun); TWeekday = (mon..fri); //not allowed; TDays = set of TDay; TWeekdays = set of TDay[mon..fri]; //not allowed Can I declare TWeekday and TWeekdays as a derivative of TDay, if so, how? Funny enough google does not yield anything (for

问题 I expect to have only 2 elements in my Set but I receive 3 elements while printing! How can I define uniqueness? public class test { public static void main(String[] args) { class bin { int a; int b; bin (int a, int b){ this.a=a; this.b=b; } public boolean Equals(bin me) { if(this.a==me.a && this.b==me.b) return true; else return false; } @Override public String toString() { return a+" "+b; } } Set<bin> q= new HashSet<bin>(); q.add(new bin(11,23)); q.add(new bin(11,23)); q.add(new bin(44,25))

问题 In Python, we can get the unique items of the list using set(list) . However doing this breaks the order in which the values appear in the original list. Is there an elegant way to get the unique items in the order in which it appears in the list. 回答1: This is an elegant way: from collections import OrderedDict list(OrderedDict.fromkeys(list)) It works if the list items are all hashable (you will know that all the list items are hashable if converting it to a set did not trigger an exception)

问题 How to define, for general parameter N:nat , finite set of N elements, $ A_{0},...A_{N-1} $ ? Is there an elegant way to do it by recursive definition? Could someone point me into good example of reasoning about such structures? 回答1: A very convenient solution is to define the n th ordinal, 'I_n as a record: Record ordinal n := { val :> nat; _ : val < n; }. that is to say, a pair of a natural number, plus a proof that such natural number is less than n , where < : nat -> nat -> bool . It is

问题 I want to find an algorithm that given a set A to find all groups of subsets that satisfy the following condition: x ∪ y ∪ .... z = A, where x, y, ... z ∈ Group and ∀ x,y ∈ Group: x ⊆ A, y ⊆ A, x ∩ y = ∅ = {} and ∀ x ∈ Group: x != ∅ Note: I hope to define it well, I'm not good with math symbols I made the following approach to search groups of two subsets only: from itertools import product, combinations def my_combos(A): subsets = [] for i in xrange(1, len(A)): subsets.append(list