本文通过自己实现的CList双向链表数据结构来完成学生管理系统，同样采用链表外排序。

• 注意：此时排序规则函数仍然定义为全局函数

自己定义CList类

文件名：List.h

-注意： POSITION不是VS默认的类型，而是重新定义为void*型

#pragma once
typedef struct SUser
{int nNumb;char sName[20];float fMath;
}DATA;struct SNode //双向链表
{DATA data;SNode* pPrev, *pNext;
};
typedef void* POSITION;class CList
{SNode* m_pHead, *m_pTail;int m_nCount;
public:POSITION GetHeadPosition() const{return m_pHead;}POSITION GetTailPosition() const{return m_pTail;}int GetCount() const{return m_nCount;}void RemoveAll();DATA& GetAt(POSITION pos){int i = -1;return ((SNode*)pos)->data;}const DATA& GetAt(POSITION pos) const{return ((SNode*)pos)->data;}DATA& GetNext(POSITION & pos) const;DATA GetPrev(POSITION & pos) const;void AddTail(DATA& data);void AddHead(DATA& data);void SetAt(POSITION pos, DATA& data) const{((SNode*)pos)->data = data;}void RemoveAt(POSITION pos);CList();~CList();
};

自己实现CList函数体

文件名：List.cpp

#include "List.h"void CList::RemoveAll()
{	SNode* p = m_pHead, *p1;while (p){p1 = p;p = p->pNext;delete p1;}m_pHead = m_pTail = nullptr;m_nCount = 0;
}DATA& CList::GetNext(POSITION & pos) const
{DATA d = ((SNode*)pos)->data;pos = ((SNode*)pos)->pNext;return d;
}DATA CList::GetPrev(POSITION & pos) const
{DATA d = ((SNode*)pos)->data;pos = ((SNode*)pos)->pPrev;return d;
}void CList::AddTail(DATA& data)
{SNode* p = new SNode;p->data = data;if (m_pTail)m_pTail->pNext = p;elsem_pHead = p;p->pNext = nullptr;p->pPrev = m_pTail;m_pTail = p;++m_nCount;
}void CList::AddHead(DATA& data)
{SNode* p = new SNode;p->data = data;if (m_pHead)m_pHead->pPrev = p; //上个头的前驱elsem_pTail = p; //若是空链表，则m_pHead m_pTail都指向pp->pNext = m_pHead; //头后继p->pPrev = nullptr; //头前驱m_pHead = p;++m_nCount;
}void CList::RemoveAt(POSITION pos)
{SNode* p = (SNode*)pos;if (p == m_pHead)p->pNext = m_pHead;elsep->pPrev->pNext = p->pNext;if (p == m_pTail)p->pPrev = m_pTail;elsep->pNext->pPrev = p->pPrev;delete p;--m_nCount;
}CList::CList()
{m_pHead = m_pTail = nullptr;m_nCount = 0;
}CList::~CList()
{RemoveAll();
}

定义CStudent类

文件名：Student.h

#pragma once
#include "List.h"typedef bool(*BY_FUNC)(DATA& q,DATA& m);class CStudent
{CList m_list;int Menu();int Input();bool Delete();void Modify();void Print();void Sort(BY_FUNC pFunc);int SortMenu();void Load();void Save();void PrintPS(POSITION* ps);bool Check(int nNumb);int FindMenu();void FindByNumb();
public:CStudent();~CStudent();void Start();
};

CStudent类函数体

文件名：Student.cpp

#define _CRT_SECURE_NO_WARNINGS #include <iostream>
#include <conio.h>
//#include <afxtempl.h>
#include "Student.h"using namespace std;int CStudent::Menu()
{system("cls");//clear screenputs("\n\t\t1、浏览所有信息");puts("\t\t2、添加信息");puts("\t\t3、删除信息");puts("\t\t4、修改信息");puts("\t\t5、查找信息");puts("\t\t0、退出");printf("\t\t请选择：");int i = 0;cin >> i;switch (i){case 1:while (SortMenu());break;case 2:while (Input());break;case 3:while (Delete());break;case 4:Modify();break;case 5:while (FindMenu());}return i;
}int CStudent::Input()
{cout << "请输入学号：";DATA d;while(true){cin >> d.nNumb;if (Check(d.nNumb))cout << "学号已存在，请重新输入：";elsebreak;}cout << "请输入姓名和数学成绩（空格间隔）：";cin >> d.sName >> d.fMath;m_list.AddTail(d);Save();Print();cout << "是否继续添加？[y/n]";rewind(stdin);char c = getchar();return c == 'y' || c == 'Y';
}bool CStudent::Delete()
{int nNumb;Print();cout << "请输入要删除的学号：";cin >> nNumb;POSITION pos = m_list.GetHeadPosition();while (pos){if (m_list.GetAt(pos).nNumb == nNumb){m_list.RemoveAt(pos);Print();cout << "删除成功！" << endl;system("pause");Save();return false;}m_list.GetNext(pos);}cout << "你输入的学号不存在，是否继续删除？[y/n]";char c = _getch();putchar(c);puts("");return 'y' == c || 'Y' == c;
}void CStudent::Modify()
{int nNumb;cout << "请输入要修改的学号：";cin >> nNumb;POSITION pos = m_list.GetHeadPosition();while (pos){DATA& d = m_list.GetAt(pos);if (d.nNumb == nNumb){cout << d.nNumb << "\t" << d.sName << "\t" << d.fMath << endl;cout << "请输入姓名和成绩：";cin >> d.sName >> d.fMath;m_list.SetAt(pos, d);Save();Print();return;}m_list.GetNext(pos);}cout << "你输入的学号不存在！" << endl;system("pause");return;
}void CStudent::Print()
{POSITION pos = m_list.GetHeadPosition();cout << "学号\t姓名\t成绩" << endl;while (pos){DATA d = m_list.GetAt(pos);cout << d.nNumb << "\t" << d.sName << "\t" << d.fMath << endl;m_list.GetNext(pos);}system("pause");
}bool byNumb(DATA& q,DATA& m)
{return q.nNumb < m.nNumb;
}bool byName(DATA& q, DATA& m)
{return strcmp(q.sName, m.sName) < 0;
}bool byMath(DATA& q, DATA& m)
{return q.fMath > m.fMath;
}void CStudent::Sort(BY_FUNC pFunc)
{int n = m_list.GetCount();POSITION* ps = new POSITION[n + 1];POSITION pos = m_list.GetHeadPosition();int i = 0, m = 0, j = 0;while (ps[i++] = pos)m_list.GetNext(pos);pos = m_list.GetHeadPosition();i = 0;while (i < n - 1){m = i;j = i + 1;while (j < n){if (pFunc(m_list.GetAt(ps[j]), m_list.GetAt(ps[m]))) //ps[j]的类型是POSITIONm = j;++j;}if (m != i){POSITION t = ps[i];ps[i] = ps[m];ps[m] = t;}++i;}PrintPS(ps);delete[] ps;
}void CStudent::PrintPS(POSITION* ps)
{int i = 0;cout << "学号\t姓名\t成绩" << endl;while (ps[i]){DATA d = m_list.GetAt(ps[i]);cout << d.nNumb << "\t" << d.sName << "\t" << d.fMath << endl;++i;}system("pause");
}bool CStudent::Check(int nNumb)
{POSITION pos = m_list.GetHeadPosition();while (pos){if (m_list.GetAt(pos).nNumb == nNumb)return true;m_list.GetNext(pos);}return false;
}void CStudent::FindByNumb()
{int nNumb;cout << "请输入要查找的学号：";cin >> nNumb;cout << "学号\t姓名\t数学成绩" << endl;POSITION pos = m_list.GetHeadPosition();int nCount = 0;while (pos){DATA d = m_list.GetNext(pos);if (d.nNumb == nNumb){cout << d.nNumb << "\t" << d.sName << "\t" << d.fMath << endl;++nCount;}}cout << "查找到 " << nCount << " 条匹配的记录。" << endl;system("pause");
}int CStudent::FindMenu()
{system("cls");puts("1、按学号查找：");puts("2、按姓名查找：");puts("3、按分数段查找：");puts("0、返回主菜单：");int i = 0;cin >> i;switch (i){case 1:FindByNumb();break;case 2:case 3:break;}return i;return 0;
}int CStudent::SortMenu()
{system("cls");puts("1.按学号排序");puts("2.按姓名排序");puts("3.按成绩排序");puts("4.不排序");puts("0.返回主菜单");int i = 0;cin >> i;BY_FUNC ps[] = { byNumb,byName,byMath };switch (i){case 1:case 2:case 3:Sort(ps[i-1]);break;case 4:Print();default:return i;}return i;
}void CStudent::Load()
{FILE* pf = fopen("stud.lv", "r");if (!pf){puts("加载文件时失败！");system("pause");return;}DATA t;while (fread(&t, 1, sizeof(DATA), pf) == sizeof(DATA))m_list.AddTail(t);fclose(pf);
}void CStudent::Save()
{FILE* pf = fopen("stud.lv", "w");if (!pf){puts("保存文件时失败！");system("pause");return;}POSITION pos = m_list.GetHeadPosition();while (pos){fwrite(pos, 1, sizeof(DATA), pf);m_list.GetNext(pos);}
}CStudent::CStudent()
{
}CStudent::~CStudent()
{
}void CStudent::Start()
{Load();while (Menu());
}

主函数

文件名：main.cpp

#include <iostream>
#include "Student.h"
int main()
{CStudent st;st.Start();return 0;
}