stl之map 排序

 1 #include <map>
 2 #include <string>
 3 using namespace std;
 4 typedef struct tagStudentInfo
 5 {
 6        int      nID;
 7        string   strName;
 8 }StudentInfo, *PStudentInfo;  //学生信息
 9 
10 int main()
11 {
12     int nSize;          //用学生信息映射分数
13     map<StudentInfo, int>mapStudent;
14     map<StudentInfo, int>::iterator iter;
15     StudentInfo studentInfo;
16     studentInfo.nID = 1;
17     studentInfo.strName = “student_one”;
18     mapStudent.insert(pair<StudentInfo, int>(studentInfo, 90));
19     studentInfo.nID = 2;
20     studentInfo.strName = “student_two”;
21 
22     mapStudent.insert(pair<StudentInfo, int>(studentInfo, 80));
23     for (iter=mapStudent.begin(); iter!=mapStudent.end(); iter++)
24         cout<<iter->first.nID<<endl<<iter->first.strName<<endl<<iter->second<<endl;
25 }
26 //以上程序是无法编译通过的，只要重载小于号，就OK了，如下：
27 
28 typedef struct tagStudentInfo
29 {
30    int      nID;
31    string   strName;
32    Bool operator < (tagStudentInfo const& _A) const
33    {   
34       //这个函数指定排序策略，按nID排序，如果nID相等的话，按strName排序
35       if(nID < _A.nID)  return true;
36       if(nID == _A.nID) return strName.compare(_A.strName) < 0;
37       return false;
38    }   
39 }StudentInfo, *PStudentInfo;  //学生信息

 1 #include <map>
 2 #include <string>
 3 using namespace std;
 4 typedef struct tagStudentInfo
 5 {
 6     int      nID;
 7     string   strName;
 8 }StudentInfo, *PStudentInfo;  //学生信息
 9 
10 class sort{
11 public:
12     bool operator() (StudentInfo const &_A, StudentInfo const &_B) const
13     {   
14         if(_A.nID < _B.nID){
　　　　　　　　 return true;
15         }else if (_A.nID == _B.nID){
　　　　　　　　 return _A.strName.compare(_B.strName) < 0;
　　　　　　}
16         return false;
17     }
18 };
19 
20 int main()
21 {
22     int nSize;          //用学生信息映射分数
23     map<StudentInfo, int, sort>mapStudent;
24     studentInfo studentInfo;
25     studentInfo.nID = 1;
26     studentInfo.strName = "student_one";
27 
28     mapStudent.insert(pair<StudentInfo, int>(studentInfo, 90));
29     studentInfo.nID = 2;
30     studentInfo.strName = "tudent_two";
31     mapStudent.insert(pair<StudentInfo, int>(studentInfo, 80));
32 }