set

问题 I have a constantly growing, potentially very large table in a Postgresql database that contains "data" from different "channels" for different "devices" eg.: Table data: id (PK) device_id (FK -> device) channel_id (FK -> channel) timestamp (TIMESTAMP) value (Float) I am using partitioning to separate the table into multiple subtables, one for each device, since I never need data for different devices in the same query. Since not all devices supply all channels, I would like to get a list of

问题 Imagine you have a struct with a bunch of members, and you want to use a particular value referenced via one of its members as the key in a set, like so: class ComplexClass { public: const string& name() const; // tons of other stuff }; struct MyStruct { ComplexClass* c; MoreStuff* x; }; struct CmpMyStruct { bool operator()(const MyStruct& lhs, const MyStruct& rhs) { return lhs.c->name() < rhs.c->name(); } }; typedef set<MyStruct, CmpMyStruct> MySet; MySet my_set; This works just fine,

问题 Assume i have an enumeration: namespace System.Windows.Forms { public enum DialogResult { None, OK, Cancel, Abort, Retry, Ignore, Yes, No } } i want to declare a "set" made up of these enumerated types ShowForm(Form frm, DialogResults allowedResults) In other languages you would declare: public DialogResults = set of DialogResult; And then i can use ShowForm(frm, DialogResult.OK | DialogResult.Retry); C# has the notion of Flags , pseudocode: [Flags] public enum DialogResults { DialogResult

问题 How can I reset a loop that iterates over a set? A common answer for iterating over a list is to reset the index you are using to access the list, however sets do not support indices. The point is to be able to iterate over a large set of objects, perform some action against each element until a result matches the result I require. The functionality I am searching for is the ability to reset a loop. Meaning restart the iteration from the beginning to ensure I visit every element again for

问题 Could anybody point me, please, what the difference is between making functor of set::insert and set::count in the below fragment? typedef std::set<std::string> s_type; typedef std::pair<s_type::iterator, bool>(s_type::*insert_fp)(const s_type::value_type&); typedef s_type::size_type(s_type::*count_fp)(const s_type::value_type&); std::vector<std::string> s_vector; std::set<std::string> s_set; std::for_each(s_vector.begin(), s_vector.end(), boost::bind(static_cast<insert_fp>(&s_type::insert),

问题 I am trying to find the index number in a list of elements that share the same data with elements in another list. These are my lists: list_A = [['A',1,'a',],['B',2,'b'],['C',3,'c'],['D',4,'d'],['E',5,'e'],['F',6,'f']] list_B = [['A','a'],['D','d']['E','e']] And the desired output should be: [0,3,4] I've tried using the set()intersection and the the index functions, but I couldn't make 'set' work with the list of lists. 回答1: You could do the following: list_A = [['A', 1, 'a', ], ['B', 2, 'b']

问题 In AMPL, I have a set which should store some similar values. But I have a "duplicate number" error. Is there any way to do that? What is the simplest method to solve this problem? The set is: set A; data: set A := 1 1 2; Thanks 回答1: Set elements should be unique in AMPL. To store duplicate values use parameter instead: set S; param A{S}; data; param: S: A := 1 1 2 1 3 2; 来源： https://stackoverflow.com/questions/26739400/ampl-error-duplicate-number-for-set

问题 This is what I am doing: String one = "some string" String two = "some string" I want to know all the characters that are in string one and two and they should come in order as they are in string one I wrote a Java program which by using Collections performs set operations on both the collection. What I would like to know that what is the complexity of performing set operations, is it polynomial time or linear time My program is here /* * To change this template, choose Tools | Templates *

问题 Given a list that could contain duplicates (like the one below), I need to be able to count Each(keyword) number of unique elements. List<String> list = new ArrayList<String>(); Set<String> set = new HashSet<String>(); list.add("M1"); list.add("M1"); list.add("M2"); list.add("M3"); set.addAll(list); System.out.println(set.size()); How do I get the count each unique element from the List? That means i want to know how many "M1" contains in List(list), how many "M2", etc. The result should be

问题 Right now, I have many MovieClips 's in my array. I want to update all the alpha values of the MovieClips in my array. Right now, I am using a for loop but this is not the fastest way to do it. Is there a way to set values for all the items in my array? Thanks! 回答1: No. ActionScript doesn't have any constructs that allow you to change properties of all elements of the array with a single line of code. There is an Array.forEach() method, but I think that would be slower than a simple for(i = 0