选修课

#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <list>
#include <map>
using namespace std;
typedef struct Student
{
 int sid; // 学号
 char sname[20]; // 姓名
} Student;

typedef struct Course
{
 int cid;//编号
 char cname[20];// 课程名
} Course;

typedef struct StudentCourse
{
 int sid;
 int cid;
} StudentCourse;

#define STUDENT_DB "stuinfo.txt"
#define COURSE_DB "courinfo.txt"
#define STUCOUR_DB "stucourinfo.txt"

void startMenu()
{
 cout << "1. 录入课程" << endl;
 cout << "2. 学生注册" << endl;
 cout << "3. 浏览课程" << endl;
 cout << "4. 查看学生" << endl;
 cout << "5. 学生选课" << endl;
 cout << "6. 浏览选课" << endl;
 cout << "7. 删除选课" << endl;
 cout << "8. 根据学生名查询选课" << endl;
 cout << "9. 根据选课查询学生" << endl;
 cout << "#. 统计排序" << endl;
}

// 录入课程
void addCourse()
{
 // 清空输入缓冲
 int c;
 while ((c = getchar()) != ' ' && c != EOF);

 Course *pCourse = (Course *)malloc(sizeof(Course));
 cout << "课程名：";
 fgets(pCourse->cname, 20, stdin);
 // 去掉最后的换行符
 pCourse->cname[strlen(pCourse->cname) - 1] = '';

 cout << "课程编号：";
 char buf[100];
 gets_s(buf);
 pCourse->cid = atoi(buf);

 FILE *fp;
 if ((fp = fopen(COURSE_DB, "ab")) == NULL)
 {
  exit(1);
 }
 fwrite(pCourse, sizeof(Course), 1, fp);
 free(pCourse);
 fclose(fp);
}

// 录入学生
void addStudent()
{
 // 清空输入缓冲
 int c;
 while ((c = getchar()) != ' ' && c != EOF);

 Student *pStudent = (Student *)malloc(sizeof(Student));
 cout << "学号：";
 char buf[100];
 fgets(buf, 100, stdin);
 pStudent->sid = atoi(buf);
 cout << "姓名：";
 gets_s(pStudent->sname);

 FILE *fp;
 if ((fp = fopen(STUDENT_DB, "ab")) == NULL)
 {
  exit(1);
 }
 fwrite(pStudent, sizeof(Student), 1, fp);
 free(pStudent);
 fclose(fp);
}

// 浏览课程
void browseCourses()
{
 FILE *fp;
 if ((fp = fopen(COURSE_DB, "rb")) == NULL)
 {
  exit(1);
 }

 Course *pCourse = (Course *)malloc(sizeof(Course));

 while (fread(pCourse, sizeof(Course), 1, fp) == 1)
 {
  cout << "课程名：" << pCourse->cname << " ";
  cout << "编号：" << pCourse->cid << endl;
 }
 free(pCourse);
 fclose(fp);
}

// 查看学生
void browseStudent()
{
 FILE *fp;
 if ((fp = fopen(STUDENT_DB, "rb")) == NULL)
 {
  exit(1);
 }
 Student *pStudent = (Student *)malloc(sizeof(Student));
 while (fread(pStudent, sizeof(Student), 1, fp) == 1)
 {
  cout << "名字：" << pStudent->sname << " ";
  cout << "学号：" << pStudent->sid << endl;
 }
 free(pStudent);
 fclose(fp);
}

// 选课
void selectCourse()
{
 // 清空输入缓冲
 int c;
 while ((c = getchar()) != ' ' && c != EOF);

 FILE *fp;
 if ((fp = fopen(STUCOUR_DB, "ab")) == NULL)
 {
  exit(1);
 }
 StudentCourse *pSC = (StudentCourse *)malloc(sizeof(StudentCourse));

 cout << "学生学号：";
 char buf[100];
 gets_s(buf);
 pSC->sid = atoi(buf);
 cout << "课程编号：";
 gets_s(buf);
 pSC->cid = atoi(buf);

 fwrite(pSC, sizeof(StudentCourse), 1, fp);
 free(pSC);
 fclose(fp);
}

// 浏览选课
void browseSelectCourse()
{
 FILE *fp;
 if ((fp = fopen(STUCOUR_DB, "rb")) == NULL)
 {
  exit(1);
 }

 StudentCourse *pSC = (StudentCourse *)malloc(sizeof(StudentCourse));

 while (fread(pSC, sizeof(StudentCourse), 1, fp) == 1)
 {
  cout << "学号：" << pSC->sid << " " << "课程编号：" << pSC->cid << endl;
 }

 free(pSC);
 fclose(fp);
}

// 删除选课
void deleteCourse()
{
 // 清空输入缓冲
 int c;
 while ((c = getchar()) != ' ' && c != EOF);

 cout << "输入学生学号：";
 char buf[100];
 gets_s(buf);

 StudentCourse *pSC1 = (StudentCourse *)malloc(sizeof(StudentCourse));
 pSC1->sid = atoi(buf);
 cout << "输入选修课编号：";
 gets_s(buf);
 pSC1->cid = atoi(buf);

 FILE *fp;
 if ((fp = fopen(STUCOUR_DB, "rb")) == NULL)
 {
  exit(1);
 }

 StudentCourse pSC2;
 list<StudentCourse> lsc;
 bool flag = false;

 while (fread(&pSC2, sizeof(StudentCourse), 1, fp) == 1)
 {
  if (pSC2.cid == pSC1->cid&&pSC2.sid == pSC1->sid)
  {
   flag = true;
  }
  else
  {
   lsc.push_back(pSC2);
  }
 }
 if (flag)
 {
  fclose(fp);
  if ((fp = fopen(STUCOUR_DB, "wb")) == NULL)
  {
   exit(1);
  }
  while (!lsc.empty())
  {
   fwrite(&lsc.front(), sizeof(StudentCourse), 1, fp);
   lsc.pop_front();
  }
 }
 free(pSC1);
 fclose(fp);
}

// 根据学生名查询选课
void browseCourseBySName()
{
 // 清空输入缓冲
 int c;
 while ((c = getchar()) != ' ' && c != EOF);

 cout << "输入姓名：";
 char buf[100];
 gets_s(buf);
 // 根据姓名查出学号
 FILE *fp;
 if ((fp = fopen(STUDENT_DB, "rb")) == NULL)
 {
  exit(1);
 }
 int sid;
 Student *pStudent = (Student *)malloc(sizeof(Student));
 while (fread(pStudent, sizeof(Student), 1, fp) == 1)
 {
  if (strcmp(pStudent->sname, buf) == 0)
  {
   sid = pStudent->sid;
   break;
  }
 }
 free(pStudent);
 fclose(fp);
 // 根据学号查出选课
 if ((fp = fopen(STUCOUR_DB, "rb")) == NULL)
 {
  exit(1);
 }
 FILE *fp1;
 if ((fp1 = fopen(COURSE_DB, "rb")) == NULL)
 {
  exit(1);
 }
 StudentCourse *pSC = (StudentCourse *)malloc(sizeof(StudentCourse));
 Course *pCourse = (Course *)malloc(sizeof(Course));
 //list<char[100]> lbuf;
 cout << "已选课程：" << endl;
 while (fread(pSC, sizeof(StudentCourse), 1, fp) == 1)
 {
  if (sid == pSC->sid)
  {
   // 根据 cid 查出课程
   while (fread(pCourse, sizeof(Course), 1, fp1) == 1)
   {
    if (pCourse->cid == pSC->cid)
    {
     //strcpy(buf, pCourse->cname);
     //lbuf.push_back(buf);
     // 打印
     cout << " " << pCourse->cname << endl;
     break;
    }
   }
  }
 }
 fclose(fp);
 fclose(fp1);
 free(pSC);
 free(pCourse);
}
// 根据选课查询学生
void browseStudentByCourse()
{
 // 清空输入缓冲
 int c;
 while ((c = getchar()) != ' ' && c != EOF);
 cout << "输入课程名：";
 char buf[100];
 gets_s(buf);

 // 课程查出课程 cid
 FILE *fp;
 if ((fp = fopen(COURSE_DB, "rb")) == NULL)
 {
  exit(1);
 }
 Course *pCourse = (Course *)malloc(sizeof(Course));
 int cid;
 while (fread(pCourse, sizeof(Course), 1, fp) == 1)
 {
  if (strcmp(pCourse->cname, buf) == 0)
  {
   cid = pCourse->cid;
   break;
  }
 }

 fclose(fp);
 free(pCourse);

 if ((fp = fopen(STUCOUR_DB, "rb")) == NULL)
 {
  exit(1);
 }
 FILE *fp1;
 if ((fp1 = fopen(STUDENT_DB, "rb")) == NULL)
 {
  exit(1);
 }

 StudentCourse *pSC = (StudentCourse *)malloc(sizeof(StudentCourse));
 Student *pStudent = (Student *)malloc(sizeof(Student));
 cout << "已选学生：" << endl;
 while (fread(pSC, sizeof(StudentCourse), 1, fp) == 1)
 {
  if (cid == pSC->cid)
  {
   while (fread(pStudent, sizeof(Student), 1, fp1) == 1)
   {
    if (pStudent->sid == pSC->sid)
    {
     cout << " " << pStudent->sname << endl;
     break;
    }
   }
  }
 }

 fclose(fp1);
 fclose(fp);
 free(pSC);
 free(pStudent);
}

bool compareNocase(list<int>& first, list<int>& second)
{
 return first.size() > second.size();
}
// 统计排序
void statisticalSorting()
{
 list<list<int>> llist;

 FILE *fp;
 if ((fp = fopen(STUCOUR_DB, "rb")) == NULL)
 {
  exit(1);
 }

 StudentCourse *pSC = (StudentCourse *)malloc(sizeof(StudentCourse));
 while (fread(pSC, sizeof(StudentCourse), 1, fp) == 1)
 {
  bool flag = false;
  // 寻找 llist 中是否存在 cid
  for (auto &l : llist)
  {
   if (l.front() == pSC->cid)
   {
    flag = true;
    l.push_back(0);
    break;
   }
  }
  if (!flag)
  {
   list<int> lint;
   lint.push_back(pSC->cid);
   llist.push_back(lint);
  }
 }
 cout << "课程编号" << " " << "选课人数" << endl;
 llist.sort(compareNocase);
 for (auto &l : llist)
 {
  cout << l.front() << " " << l.size() << endl;
 }
}
int main()
{
 while (1)
 {
  startMenu();
 start:
  cout << "请选择：";
  int ch;
  ch = getchar();
  switch (ch)
  {
  case '1':
   addCourse();
   break;
  case '2':
   addStudent();
   break;
  case '3':
   browseCourses();
   break;
  case '4':
   browseStudent();
   break;
  case '5':
   selectCourse();
   break;
  case '6':
   browseSelectCourse();
   break;
  case '7':
   deleteCourse();
   break;
  case '8':
   browseCourseBySName();
   break;
  case '9':
   browseStudentByCourse();
   break;
  case '#':
   // todo 统计排序
   statisticalSorting();
   break;
  case ' ':
   goto start;
  default:
   cout << "非法输入" << endl;
  }

 }

 return 0;
}