Question

这是要比较的字符串，lastname + firstName和id comp是公共的，我的排序方法不起作用，我无法找到代码失败的地方，我应该让学生在订单中列出

comp=new char[strlen(lName)+strlen(fName)+strlen(id)+1];

这是我的学生构造函数：

Student::Student(char * first, char * last, char *i,char * stand, int credit, double g, Date * d, Date * matricDate){
        lName=last;
        fName=first;
        id=i;
        standing=stand;
        credits=credit;
        gpa=g;
        dob=d;
        matDate=matricDate;
        comp=new char[strlen(lName)+strlen(fName)+strlen(id)+1];
        sprintf(comp,"%s%s%s",lName,fName,id);
};

这是我重载的运算符

 bool Student::operator<(const Student &second){
                if(comp<second.comp){
                        return true;
                }else{
                        return false;
                }
        };

我有学生名单：

 vector<Student *> roster_list;

我像这样添加学生：

void Roster::addStudent(Student *student){

        roster_list.push_back(student); 

        };

这是我的排序：

void Roster::mySort(){
        sort(roster_list.begin(),roster_list.end());
};

我的主要：

#include<iostream>
#include"Roster.cpp"
#include "Date.cpp"
#include "Student.cpp"

using namespace std;


int main(){

        Roster *r=new Roster();
        Date *d=new Date(12,05,1987);
        Student *st=new Student("Jason", "Sam", "124542", "sophomore", 34, 4.0, d,d);
        Student *st2=new Student("Ahmad", "Khan", "23452", "freshman", 34, 4.0, d,d);

        Student *st3=new Student("Selam", "Can", "23431", "freshman", 34, 3.0, d,d);
        Student *st4=new Student("Andrew", "Rosenberg", "34523", "Senior", 34, 4.0, d,d);
        Student *st5=new Student("Selam", "Can", "23431", "freshman", 34, 3.0, d,d);


        r->addStudent(st);
        r->addStudent(st2);
        r->addStudent(st3);
        r->addStudent(st4);

        // Student 3 and 5 are same 
        // == operator check
        if(*st3==*st5){
                cout<<"Students are same \n";
        }

        // != overloading operator check
        if(*st3!=*st4){
                cout<<"Students are different\n";
        }

        cout<<"################Before Sorting###############\n";
        r->toString();
        cout<<"################After Sorting###############\n";
        r->mySort();
        r->toString();



        cout<<"\n"<<st->getComp();
        cout<<"\n"<<st3->getComp();

        return 0;
}

输出：

Students are same 
Students are different
################Before Sorting###############
Student Info:Jason      Sam     124542  sophomore       4
Birth Date: December 5, 1987
Matric Date: December 5, 1987
Student Info:Ahmad      Khan    23452   freshman        4
Birth Date: December 5, 1987
Matric Date: December 5, 1987
Student Info:Selam      Can     23431   freshman        3
Birth Date: December 5, 1987
Matric Date: December 5, 1987
Student Info:Andrew     Rosenberg       34523   Senior  4
Birth Date: December 5, 1987
Matric Date: December 5, 1987
################After Sorting###############
Student Info:Jason      Sam     124542  sophomore       4
Birth Date: December 5, 1987
Matric Date: December 5, 1987
Student Info:Ahmad      Khan    23452   freshman        4
Birth Date: December 5, 1987
Matric Date: December 5, 1987
Student Info:Selam      Can     23431   freshman        3
Birth Date: December 5, 1987
Matric Date: December 5, 1987
Student Info:Andrew     Rosenberg       34523   Senior  4
Birth Date: December 5, 1987
Matric Date: December 5, 1987

SamJason124542
CanSelam23431

我试过这个

bool StudentSort(Student* lhs, Student* rhs) {
    return (*lhs)<(*rhs);
}



void Roster::mySort(){
        sort(roster_list.begin(),roster_list.end(),StudentSort);
};

仍然无法正常工作，我收到编译错误我有gcc版本4.4.7 20120313（Red Hat 4.4.7-3）（GCC）

这是我在尝试之后得到的错误：

Roster.cpp: In member function ‘void Roster::mySort()’:
Roster.cpp:69: error: argument of type ‘bool (Roster::)(Student*, Student*)’ does not match ‘bool (Roster::*)(Student*, Student*)’

Answer 1

您似乎已将bool StudentSort作为Roster的成员函数。你应该让它成为非会员。

另外，您应该制作operator< const，以便它可以对LHS和RHS上的const个引用进行操作。比较运算符改变操作数是没有意义的。您也可以简化它：

bool Student::operator<(const Student& second) const {
    return comp<second.comp;
}

有了这个，您可以更改比较函数以指向const：

bool StudentSort(const Student* lhs, const Student* rhs) { .... }

修改由于@RetiredNinja已指针指出，Student::comp为char*，因此您的比较运算符正在比较指针。这不太可能是你想要的。解决这个问题和你的大多数其他问题的方法是根本不使用指针。特别是如果你不明白它们是什么。我建议std::string使用comp。

将学生与超载＆lt;进行比较操作者

1 个答案: