在双重链接列表中的QuickSort算法

我想用姓氏对QuickSort的算法进行对列表进行排序

在这一部分中，链的值交换

void swap(string* a, string* b){

cout<<"A and B are "<<*a<<" - "<<*b<<endl;
string t = *a;
*a = *b;
cout<<" A is ->"<<*a<<endl;
*b= t;
cout<<"B is ->"<<*b<<endl;
}

这是进行分区的地方。我注意到，当 * i和 * j取值时，它们是完全相同的名称，因此无法以后进行比较。在我看来，如果它是一个数字，那么此列表有效，但是当它是字符串时，此错误发生。

User *i = lower;

，但这在结尾不起作用，因为程序崩溃了，但是如果您更改字符串的值

User* partition(User *lower, User *high){
cout<<"Lower ->  "<<lower->lastname<<endl;
cout<<"High ->  "<<high->lastname<<endl;
string  pivot = high->lastname;
User *i = bajo->prev;
 for (User *j = lower; j != high; j = j->next)
{
    if (j->lastname.compare(pivot)< 0)
    {
        i = (i == NULL)? lower : i->next;
        cout<<"Atention J e I valen ->"<<i->lastname<<" - "<<j->lastname<<endl;
        swap(&(i->lastname), &(j->lastname));
    }
}
i = (i == NULL)? lower : i->lastname; // Similar to i++
swap(&(i->lastname), &(alto->lastname));
return i;
}

我失败了什么？我该如何真正采用所需的价值。

编辑：

这是源代码

#include <iostream>
#include<iomanip>
#include <string>
#include<cstdlib>
using namespace std;
class User
{
public :
    string lastname;
    User *next;
    User *prev;
    User()
    {
        lastname= "";
        next=NULL;
        prev=NULL;
    }
    int empty(User *listt)
    {
        if(listt ==  NULL)
        {
            return 1;
        }
        else
        {
            return 0;
        }
    }

    User *Insert(User *listt, string lastName)
    {
        User *temp = new User();
        if(empty(listt))
        {
            temp->lastname=lastName;
            listt = temp;
        }
        else
        {
            temp->lastname=lastName;
            listt->prev=temp;
            temp->next=listt;
            listt=temp;
        }
        return listt;
    }
    void swap(string* a, string* b)
    {
        string t = *a;
        *a = *b;
        *b= t;
    }
    User* partition(User* lower, User* high)
    {
        cout<<"Lower ->  "<<lower->lastname<<endl;
        cout<<"High ->  "<<high->lastname<<endl;
        string  pivot = high->lastname;
        User *i = lower->prev;
        for (User *j = lower; j != high; j = j->next)
        {
            if (j->lastname.compare(pivot)< 0)
            {
                i = (i == NULL)? lower : i->next;
                swap(&(i->lastname), &(j->lastname));
            }
        }
        i = (i == NULL)? lower : i->next; // Similar to i++
        swap(&(i->lastname), &(high->lastname));
        return i;
    }
    User *Last(User *listt)
    {
        User *temp = listt;
        while(temp && temp ->next)
            temp=temp->next;
        return temp;

    }
    void _quickSort( User* lower, User* high)
    {
        if(high != NULL && lower != high&&lower!= high->next)
        {
            User *p = partition(lower,high);
            _quickSort(lower,p->next); //I change this part
            _quickSort(p->next,high);
        }
    }
    void quickSort(User *listt)
    {
        User *h = Last(listt);
        _quickSort(listt, h);

    }
    User *Display(User *listt)
    {
        if(empty(listt))
        {
            cout<<"List empty"<<endl;
        }
        else
        {
            User *temp = new User();
            temp = listt;
            while(temp!= NULL)
            {
                cout<<"The last name is -> "<<temp->lastname<<endl;
                temp=temp->next;
            }
        }
        return listt;

    }
};
int main()
{
    User *listt = NULL;
    User y;
    bool exit = false;
    int opc;
    string lastName;
    while(!exit)
    {
        cout<<"1.-Insert an element"<<endl;
        cout<<"2.-Sort element-(Quicksort)"<<endl;
        cout<<"3.-Show elements"<<endl;
        cout<<"4.-Exitt"<<endl;
        cin>>opc;
        switch(opc)
        {
        case 1:
            cout<<"Inser your last name"<<endl;
            cin>>lastName;
            listt=y.Insert(listt,lastName);
            system("pause");
            system("cls");
            break;
        case 2:
            cout<<"Sorting...."<<endl;
            y.quickSort(listt);
            system("pause");
            system("cls");
            break;
        case 3:
            cout<<"Display..."<<endl;
            y.Display(listt);
            system("pause");
            system("cls");
            break;
        case 4:
            exit = true;
            break;

        }


    }


}