p-7.cpp

一个实现对学生成绩输入

#include <iostream.h> 
#include <string.h> 
#include <fstream.h> 

struct student 
{ 
char num[10]; 
char name[20]; 
int age; 
int score; 
struct student *next; 
}; 
class grade 
{ 
private : 
struct student * head,* last;  
public : 
void init(); 
void insert(); 
int delet(); 
int select(); 
int modify(); 
int display(); 
int total(); 
void savefile(); 
void quit(); 
}; 
  
void grade::init() 
{ 
cout<<"************************************主菜单************************************\n"<<endl; 
cout<<"\t1输入学生资料\t\t\t\t\t2删除学生资料\n"<<endl; 
cout<<"\t3查询学生资料\t\t\t\t\t4修改学生资料\n"<<endl; 
cout<<"\t5显示学生资料\t\t\t\t\t6统计学生成绩\n"<<endl; 
cout<<"\t7保存学生资料\t\t\t\t\t0退出系统\n"<<endl; 
cout<<"******************************************************************************\n"<<endl; 
head=last=NULL; 
} 

void grade::insert() 
{ 
struct student * p; 
//p=(struct student *)malloc(sizeof(struct student)); 
p = new student; 
cout<<"please insert num,name,age,score"<<endl; 
cin>>p->num>>p->name>>p->age>>p->score; 
if (head==NULL) {head=p;last=p;last->next=NULL;} 
else 
{ 
last->next=p; 
last=p; 
last->next=NULL; 
} 
} 

int grade::delet() 
{ 
char* dnum ;/* 要删除的学号*/ 
struct student * p, *p1; 
cout<<"请你输入要删除的学号:"<<endl; 
cin>>dnum; 
if (head==NULL) {cout<<"no student can be found"<<endl;return 0;} 
if (head->next=NULL && strcpy(head->num,dnum)==0)/* 只有一个记录且是要删除的数据*/ 
{head=NULL;last=NULL;return 0;} 
p=head; 
while(p->next!=NULL) 
{ 
p1=p->next; 
if (strcpy(p->num,dnum)==0 && p1->next==NULL )/* 数据在到数第二的位置*/ 
{p->next=last;cout<<"one student has been deleted"<<endl;return 0;} 
else if (p1==NULL && strcpy(p1->num,dnum)==0)/* 数据在到数第一的位置*/ 
 {p->next=NULL;last=p;cout<<"one student has been deleted"<<endl;return 0;} 
else if (strcpy(p->num,dnum)==0 && p1->next!=NULL )  
{p->next=p1->next;p=p1;/*p=p1;等一下次执行p=p->next;实际p已经指到p1->next了*/ 
cout<<"one student has been deleted"<<endl;return 0;} 
p=p->next; 
} 
cout<<"no student can be found"<<endl;return 0; 
} 

int grade::select() 
{ 
char* snum;/* 要查询的学号*/ 
struct student * p; 
cout<<"请你输入要查询的学号:"<<endl; 
cin>>snum; 
p=head; 
while(p!=NULL) 
{ 
if (strcpy(p->num,snum)==0) 
{ 
cout<<"num:"<<p->num<<"\nname"<<p->name<<"\nage"<<p->age<<"\nscore"<<p->score<<endl; 
return 0; 
} 
p=p->next; 
} 
cout<<"no student can be found"<<endl;return 0; 
} 

int grade::modify() 
{ 
char* mnum;/* 要修改的学号*/ 
struct student *p; 
cout<<"请你输入要修改的学号:"<<endl; 
cin>>mnum; 
p=head; 
while(p!=NULL) 
{ 
if (strcpy(p->num,mnum)==0) 
{ 
cout<<"please insert the new name,age,score"<<endl; 
cin>>p->name>>p->age>>p->score; 
cout<<"one student has been modify"<<endl; 
return 0; 
} 
p=p->next; 
} 
cout<<"no student can be found"<<endl;return 0; 
} 

int grade::display() 
{ 
struct student *p; 
p=head; 
if (head==NULL) {cout<<"no student can be found"<<endl;return 0;} 
while(p!=NULL) 
{ 
cout<<"num:"<<p->num<<"\nname"<<p->name<<"\nage"<<p->age<<"\nscore"<<p->score<<endl; 
p=p->next; 
} 
return 0; 
} 

int grade::total() 
{ 
int max,jg_num=0; 
struct student *p; 
p=head; 
if (head==NULL) {cout<<"no student can be found"<<endl;return 0;} 
max=p->score; 
while(p!=NULL) 
{ 
if (p->score>max) max=p->score; 
if (p->score<60) jg_num++; 
p=p->next; 
} 
cout<<"the high score:"<<max<<endl; 
cout<<"不及格学生人数:"<<jg_num<<endl; 
return 0; 
} 

void grade::savefile() 
{ 
struct student * p; 
ifstream input; 
input.open("student"); 
p=head; 
while(p!=head) 
{ 
input>>p->num>>p->name>>p->age>>p->score; 
p=p->next;  
} 
cout<<"the file save over"<<endl; 
} 

int main() 
{ 
int choice; 
grade Grade; 
Grade.init(); 
while(1) 
{ 
cin>>choice; 
switch(choice) 
{ 
case 1: 
Grade.insert();  

break; 
case 2: 
Grade.delet();  
break; 
case 3: 
Grade.select();  
break; 
case 4: 
Grade.modify();  
break; 
case 5: 
Grade.display(); 
break; 
case 6:Grade.total();  
break; 
case 7: 
Grade.savefile(); 
break; 
case 0:  
return 0;  
} 
} 
return 0; 
}