stdset

问题 I have used find_if before with lists and vectors in C++ and it has worked fine. But now, when I try to use it with sets I get the following error: error: no matching function for call to ‘find_if(std::set<A, Acmp>::iterator, std::set<A, Acmp>::iterator, <unresolved overloaded function type>)’| My class is the following: bool searchForA(A i) { return (i.getVal() > 0); } void B::findA() { set<A, Acmp> cont; set<A, Acmp>::iterator it; A *a1 = new A(5); A *a2 = new A(7); cont.insert(*a1); cont

问题 I need to copy std::set to std::vector : std::set <double> input; input.insert(5); input.insert(6); std::vector <double> output; std::copy(input.begin(), input.end(), output.begin()); //Error: Vector iterator not dereferencable Where is the problem? 回答1: You need to use a back_inserter : std::copy(input.begin(), input.end(), std::back_inserter(output)); std::copy doesn't add elements to the container into which you are inserting: it can't; it only has an iterator into the container. Because

问题 I have a bunch of data full of duplicates and I want to eliminate the duplicates. You know, e.g. [1, 1, 3, 5, 5, 5, 7] becomes [1, 3, 5, 7]. It looks like I can use either std::map or std::set to handle this. However I'm not sure whether it's faster to (a) simply insert all the values into the container, or (b) check whether they already exist in the container and only insert if they don't - are inserts very efficient? Even if there's a better way... can you suggest a fast way to do this?

问题 I'm new to C++. I'd like to know how experienced coders do this. what I have: set<int> s; s.insert(1); s.insert(2); s.insert(3); s.insert(4); s.insert(5); for(set<int>::iterator itr = s.begin(); itr != s.end(); ++itr){ if (!(*itr % 2)) s.erase(itr); } and of course, it doesn't work. because itr is incremented after it is erased. does it mean Itr has to point to the begin of the set everytime after i erase the element from the set? 回答1: for(set<int>::iterator itr = s.begin(); itr != s.end(); )

问题 Consider the simple program below, which attempts to iterate through the values of a set using NON-const references to the elements in it: #include <set> #include <iostream> class Int { public: Int(int value) : value_(value) {} int value() const { return value_; } bool operator<(const Int& other) const { return value_ < other.value(); } private: int value_; }; int main(int argc, char** argv) { std::set<Int> ints; ints.insert(10); for (Int& i : ints) { std::cout << i.value() << std::endl; }

问题 The following code: #include <iostream> #include <set> #include <algorithm> std::set<int> s; int main() { s.insert(1); s.insert(2); std::remove(s.begin(), s.end(), 1); } does not compile with gcc 4.7.2: $ LANG=C g++ test.cpp In file included from /usr/include/c++/4.7/algorithm:63:0, from test.cpp:3: /usr/include/c++/4.7/bits/stl_algo.h: In instantiation of '_FIter std::remove(_FIter, _FIter, const _Tp&) [with _FIter = std::_Rb_tree_const_iterator<int>; _Tp = int]': test.cpp:12:38: required

问题 I have been trying to find the intersection between two std::set in C++, but I keep getting an error. I created a small sample test for this #include <iostream> #include <vector> #include <algorithm> #include <set> using namespace std; int main() { set<int> s1; set<int> s2; s1.insert(1); s1.insert(2); s1.insert(3); s1.insert(4); s2.insert(1); s2.insert(6); s2.insert(3); s2.insert(0); set_intersection(s1.begin(),s1.end(),s2.begin(),s2.end()); return 0; } The latter program does not generate

问题 I am using a std::set to implement a specific algorithm. The set had duplicates in it, so I assume I had to overload the operator. The overload looks like this. class Vec3f { ... bool operator () ( const Vector3f& v0, const Vector3f& v1 ) const { float epsilon = 1e-7; return ((v1[0] - v0[0]) > epsilon) && ((v1[1] - v0[1]) > epsilon) && ((v1[2] - v0[2]) > epsilon); } ... "Vec3f.h" int main(){ ... std::set<Vec3f,Vec3f> visited; ... } I overloaded it so I could use the < operator needed in std:

问题 This is the code: struct comp { bool operator()(Reputation *one, Reputation *two) { if (one->Amount < 0 && two->Amount >= 0) return false; if (one->Amount >= 0 && two->Amount < 0) return true; if (one->Amount >= 0) return one->Amount <= two->Amount; else return one->Amount >= two->Amount; } }; And this is the problem: Debug Assertion Failed! File: ..\VC\include\xtree Line: 638 Expression: invalid operator< After that, I can choose "Abort", "Retry" or "Ignore". If I choose ignore many more

问题 I have a map for keeping the team name and players of the team std:pair<std::string, std::vector<std::string> > and a set of pointers to players to keep the players sorted in descending order by wins. And there's the catch - one player can participate in more than one team. class Player { public: int wins; std::string name; Player() {} Player(std::string name) : wins(0), name(name) {} bool operator<(const Player* rhs) const { return this->wins > rhs->wins; } bool operator()(const Player* lhs,