vector 排序方法sort的使用
使用vector的sort方法，有两种形式，一种是在类内部使用操作符重载实现，一种是在类外面写一个比较函数。但是sort方法无法直接传入其它形参，在需要动态排序相对某个人的位置时，采取了间接通过静态变量的方法。为防止并发量巨大时，静态变量无法及时改变而产生错误数据，故用一循环去验证等待赋值，排完序后再还原为初始值。
1 #include <iostream> 2 #include <string> 3 #include <cmath> 4 #include <vector> 5 6 using namespace std; 7 8 double calc_distance(double _long1,double _lat1,double _long2,double _lat2) 9 { 10 double rad = 6371.0; 11 const double PI = 3.14159265358979323846; 12 double long1 = _long1/180.0*PI; 13 double lat1 = _lat1/180.0*PI; 14 double long2 = _long2/180.0*PI; 15 double lat2 = _lat2/180.0*PI; 16 return rad*(acos(cos(lat2)*cos(lat1)*cos(long2-long1)+sin(lat2)*sin(lat1))); 17 } 18 class User 19 { 20 private: 21 int id; 22 double longitude; 23 double latitude; 24 25 public: 26 int getid(){return id;} 27 double getlongitude(){return longitude;} 28 double getlatitude(){return latitude;} 29 User(int _id,double _longitude,double _latitude) 30 { 31 id = _id; 32 longitude = _longitude; 33 latitude = _latitude; 34 } 35 36 bool operator<(const User& obj) const 37 { 38 return id < obj.id; 39 } 40 41 bool operator>(const User& obj) const 42 { 43 return id > obj.id; 44 } 45 46 friend bool sort_by_distance(const User& obj1,const User& obj2); 47 friend bool sort_by_id(const User& obj1,const User& obj2); 48 }; 49 50 static double _longitude = 0.0; 51 static double _latitude = 0.0; 52 53 bool sort_by_distance(const User& obj1,const User& obj2) 54 { 55 return calc_distance(obj1.longitude,obj1.latitude,_longitude,_latitude)< calc_distance(obj2.longitude,obj2.latitude,_longitude,_latitude); 56 } 57 58 bool sort_by_id(const User& obj1,const User& obj2) 59 { 60 return obj1.id < obj2.id; 61 } 62 int main() 63 { 64 vector<User> vect; 65 User test1(3,20.1,20.1); 66 User test2(2,30.1,30.1); 67 User test3(1,40.1,40.1); 68 User test4(4,50.1,50.1); 69 User test5(5,60.1,60.1); 70 vect.push_back(test1); 71 vect.push_back(test2); 72 vect.push_back(test3); 73 vect.push_back(test4); 74 vect.push_back(test5); 75 while(true) 76 { 77 if(_longitude == 0.0 && _latitude == 0.0) 78 { 79 _longitude = 30.1; 80 _latitude = 30.1; 81 break; 82 } 83 } 84 85 sort(vect.begin(),vect.end(),sort_by_distance); 86 //sort(vect.begin(),vect.end(),sort_by_id); 87 //sort(vect.begin(),vect.end(),less<User>()); 88 //sort(vect.begin(),vect.end(),greater<User>()); 89 90 _longitude = 0.0; 91 _latitude = 0.0; 92 93 vector<User>::iterator it = vect.begin(); 94 while(it != vect.end()) 95 { 96 cout<<"ID:"<<it->getid()<<"\tLong:"<<it->getlongitude()<<"\tLat:"<<it->getlatitude()<<endl; 97 it++; 98 } 99 100 }
