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Questions tagged [stdset]

In C++, `std::set`s are a kind of associative container that stores unique elements, and in which the elements themselves are the keys.

294 questions
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Can I make a constexpr object of std::set?

I need a const object of std::set, which will be used in many other cpp files. Since that the initializing-order of each parts of the app is undefined, I may get a empty set when I initialize other const objects with this std::set obj. So, I want…
Leon
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How to sort std::set according to the second element?

Given n points in a two-dimensional space, sort all the points in ascending order. (x1,y1) > (x2,y2) if and only if (x1>x2) or (x1==x2 && y1
user11376749
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Error: passing x as 'this' argument of x discards qualifiers

I'm writing a HeartbeatManager for my application (in visual studio). The data of 1 heartbeat is stored in a Heart object. The Heart objects are stored in an std::set. For this reason, I am implementing the operator=, operator< and operator>…
Cpt. Pineapple
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Reverse iterator is being advanced by std::set::erase

I am trying to erase the element that I just traversed into. I initially forgot to store the return value of s1.erase(... inside the for loop to ultimately set the condition to exit the loop. With the way the code is right now, I expected the loop…
MoD
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C++ set with a comparator for sort and another for uniqueness

Edge is a class with 3 fields: weight, from_vertex, to_vertex. I want to create a set containing all unique edges in a graph. (If from_vertex and to_vertex are swapped -and weights are equal-, it is still the same edge.) Also, I want this set be…
Den
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Error with custom struct: "VS 2015 error C2678: binary '<': no operator found which takes a left-hand operand of type 'const Node'"

I am attempting to create an implementation of the A* algorithm on a 2D grid and have arrived stuck at the point where I am needing to create a set of a node's neighbours. Below are the structs I am using. // Holds values for x and y locations on…
user4415680
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Ordering a set of pairs in decending order by the first value and then alphabetically by the second value

I have a set of pairs of integers and sets, e.g: items = {(2,{"A", "B", "C"}),(3,{"C"}),...} I have it set up this way because stl sets can be easily ordered by writing a comparator for the declaration, I do not know how to write such a function to…
Daryl Drake
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Count distinct elements from a concurrently read stream

I have multiple listeners threads reading a stream of messages (Kafka). Each message has an identifier. The consumers/stream guarantees at-least once consumption. At most of the time, the stream would provide the message exactly once. The count of…
Mukul Gupta
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Make std::set to use conversion operator when compare elements

Currently I use std::map to save key/value pairs: #include using K = int; struct P {}; // some useful payload int main() { std::map< K, P const > m; m.insert({1, {}}); auto it = m.find(1); // access: it->first; …
Tomilov Anatoliy
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why is std::set `lower_bound` a `const_iterator` in this c++ example

I don't understand why this doesn't compile. #include #include struct Foo { struct Rec { std::string _s; Rec(const std::string& s) : _s(s) {} bool operator==(const Rec& r) const { return _s ==…
jkj yuio
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How to initialize a map from a set

I want to set the keys of a std::map using the elements of a std::set (or a std::vector). Something like the following... std::set keys = { 3,4,6 }; std::map results(keys); // syntax error Can this be done without explicitly…
Brent Bradburn
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std multiset insert and keep length fixed

I am interested in inserting elements in a std::multiset but I would like to keep the set fixed length. Every time an element is inserted, the last element will be removed. I came up with the following solution int main(){ …
JVn
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Std::map \ std::set contain duplicate keys

I have an issue and though I understand, that is kind of a stupid question to ask, but I failed to find a solution on my own. So, I'm trying to accumulate a container with unique values of a structure I have. struct Symbol { D2D1_RECT_F bbox; …
Aleksandr Kurinnoi
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Faster lookup than std::set

I need a faster membership lookup for some legacy packet processing code which needs to identify if a packet with a particular ID is in a particular list. The list is only updated every few seconds while the packet matching happens very very often,…
Danny
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