如何sortingSTL向量？
我想sorting一个vector
vector<myClass> object;
myclass包含很多intvariables。 我怎样才能在myClass任何特定的数据variables上sorting我的vector 。
重载less于操作符，然后sorting。 这是我在网上find的一个例子
class MyData { public: int m_iData; string m_strSomeOtherData; bool operator<(const MyData &rhs) const { return m_iData < rhs.m_iData; } }; std::sort(myvector.begin(), myvector.end());
来源： 这里
std::sort(object.begin(), object.end(), pred());
其中， pred()是定义myclass对象顺序的函数对象。 或者，你可以定义myclass::operator< 。
例如，你可以传递一个lambda：
std::sort(object.begin(), object.end(), [] (myclass const& a, myclass const& b) { return av < bv; });
或者如果你用C ++ 03，函数对象方法（ v是你想要sorting的成员）：
struct pred { bool operator()(myclass const & a, myclass const & b) const { return av < bv; } };
指向成员的指针允许您编写一个比较器，它可以与您的类的任何数据成员一起使用：
#include <algorithm> #include <vector> #include <string> #include <iostream> template <typename T, typename U> struct CompareByMember { // This is a pointer-to-member, it represents a member of class T // The data member has type U UT::*field; CompareByMember(UT::*f) : field(f) {} bool operator()(const T &lhs, const T &rhs) { return lhs.*field < rhs.*field; } }; struct Test { int a; int b; std::string c; Test(int a, int b, std::string c) : a(a), b(b), c(c) {} }; // for convenience, this just lets us print out a Test object std::ostream &operator<<(std::ostream &o, const Test &t) { return o << tc; } int main() { std::vector<Test> vec; vec.push_back(Test(1, 10, "y")); vec.push_back(Test(2, 9, "x")); // sort on the string field std::sort(vec.begin(), vec.end(), CompareByMember<Test,std::string>(&Test::c)); std::cout << "sorted by string field, c: "; std::cout << vec[0] << " " << vec[1] << "\n"; // sort on the first integer field std::sort(vec.begin(), vec.end(), CompareByMember<Test,int>(&Test::a)); std::cout << "sorted by integer field, a: "; std::cout << vec[0] << " " << vec[1] << "\n"; // sort on the second integer field std::sort(vec.begin(), vec.end(), CompareByMember<Test,int>(&Test::b)); std::cout << "sorted by integer field, b: "; std::cout << vec[0] << " " << vec[1] << "\n"; }
输出：
sorted by string field, c: xy sorted by integer field, a: yx sorted by integer field, b: xy
就像在其他答案中解释的那样，你需要提供一个比较function。 如果你想保持该函数的定义接近sort调用（例如，如果这只是有意义的），你可以用boost::lambda来定义它。 使用boost::lambda::bind来调用成员函数。
例如按成员variables或函数data1sorting：
#include <algorithm> #include <vector> #include <boost/lambda/bind.hpp> #include <boost/lambda/lambda.hpp> using boost::lambda::bind; using boost::lambda::_1; using boost::lambda::_2; std::vector<myclass> object(10000); std::sort(object.begin(), object.end(), bind(&myclass::data1, _1) < bind(&myclass::data1, _2));
这是我一般解决这个问题的方法。 它扩展了Steve Jessop的答案，删除了明确设置模板参数的要求，并添加了使用functoins和指向方法的指针（getters）
#include <vector> #include <iostream> #include <algorithm> #include <string> #include <functional> using namespace std; template <typename T, typename U> struct CompareByGetter { U (T::*getter)() const; CompareByGetter(U (T::*getter)() const) : getter(getter) {}; bool operator()(const T &lhs, const T &rhs) { (lhs.*getter)() < (rhs.*getter)(); } }; template <typename T, typename U> CompareByGetter<T,U> by(U (T::*getter)() const) { return CompareByGetter<T,U>(getter); } //// sort_by template <typename T, typename U> struct CompareByMember { UT::*field; CompareByMember(UT::*f) : field(f) {} bool operator()(const T &lhs, const T &rhs) { return lhs.*field < rhs.*field; } }; template <typename T, typename U> CompareByMember<T,U> by(UT::*f) { return CompareByMember<T,U>(f); } template <typename T, typename U> struct CompareByFunction { function<U(T)> f; CompareByFunction(function<U(T)> f) : f(f) {} bool operator()(const T& a, const T& b) const { return f(a) < f(b); } }; template <typename T, typename U> CompareByFunction<T,U> by(function<U(T)> f) { CompareByFunction<T,U> cmp{f}; return cmp; } struct mystruct { double x,y,z; string name; double length() const { return sqrt( x*x + y*y + z*z ); } }; ostream& operator<< (ostream& os, const mystruct& ms) { return os << "{ " << ms.x << ", " << ms.y << ", " << ms.z << ", " << ms.name << " len: " << ms.length() << "}"; } template <class T> ostream& operator<< (ostream& os, std::vector<T> v) { os << "["; for (auto it = begin(v); it != end(v); ++it) { if ( it != begin(v) ) { os << " "; } os << *it; } os << "]"; return os; } void sorting() { vector<mystruct> vec1 = { {1,1,0,"a"}, {0,1,2,"b"}, {-1,-5,0,"c"}, {0,0,0,"d"} }; function<string(const mystruct&)> f = [](const mystruct& v){return v.name;}; cout << "unsorted " << vec1 << endl; sort(begin(vec1), end(vec1), by(&mystruct::x) ); cout << "sort_by x " << vec1 << endl; sort(begin(vec1), end(vec1), by(&mystruct::length)); cout << "sort_by len " << vec1 << endl; sort(begin(vec1), end(vec1), by(f) ); cout << "sort_by name " << vec1 << endl; }
