C2678 二进制“<”: 没有找到接受“const ***”类型的左操作数的运算符解决办法

正确代码如下：

#include<iostream>
#include<string>
#include<map>

using namespace std;
/*仿函数的应用*/
typedef struct tagStudentinfo
{
    int      niD;
    string   strName;
}Studentinfo, *PStudentinfo; //学生信息  

class sort
{
public:
    bool operator() (Studentinfo const &_A, Studentinfo const &_B) const
    {
        if (_A.niD < _B.niD)
            return true;
        if (_A.niD == _B.niD)
            return _A.strName.compare(_B.strName) < 0;
        return false;
    }
};
void main() {
    map<int,Studentinfo> mapStudent;
    map<int,Studentinfo>::iterator mit;

    Studentinfo student1;
    student1.niD = 1;
    student1.strName = "cc";
    mapStudent.insert(pair<int,Studentinfo>(80,student1));

    Studentinfo student2;
    student2.niD = 1;
    student2.strName = "aa";
    mapStudent.insert(pair<int,Studentinfo>(90,student2));

    Studentinfo student3;
    student3.niD = 2;
    student3.strName = "dd";
    mapStudent.insert(pair<int,Studentinfo>(100,student3));

    cout << "students info:" << endl;;
    for (mit = mapStudent.begin(); mit != mapStudent.end(); mit++) {
        cout << mit->second.niD<< "," << mit->second.strName<<"," << mit->first << endl;
    }
    system("pause");
}