学生信息链表，建立，插入，删除，遍历，查找，修改，最大（小）值，平均

/【例11-10】建立一个学生成绩信息（包括学号、姓名、成绩）的单向链表，学生数据按学号由小到大顺序排列，要求实现对成绩信息的插入、修改、删除和遍历操作。/

/* 用链表实现学生成绩信息的管理 */

include<stdio.h>

include<stdlib.h>

include<string.h>

struct stud_node{
int num;
char name[20];
int score;
struct stud_node next;
};
struct stud_node * Create_Stu_Doc(); / 新建链表 */
struct stud_node * InsertDoc(struct stud_node * head, struct stud_node stud); / 插入 /
struct stud_node * DeleteDoc(struct stud_node * head, int num); / 删除 /
void Print_Stu_Doc(struct stud_node * head); / 遍历 */

struct stud_node * Find(struct stud_node * head, int num); /查找/
struct stud_node * Modify(struct stud_node * head, int num, int score); /修改成绩/
struct stud_node * Max(struct stud_node * head); /求最高分数的学生记录/
struct stud_node * Min(struct stud_node * head); /求最低分数的学生记录/
double Ave(struct stud_node * head); /求平均分/
void Save(struct stud_node * head);
struct stud_node *Read();

typedef struct stud_node *LNode;
LNode head,p;

int main(void)
{
struct stud_node *head=NULL, *p;
int choice, num, score;
char name[20];
int size = sizeof(struct stud_node);

do{
printf("1:Create 2:Insert 3:Delete 4:Print 5:Modify 6:Find 7:Max 8:Save 9:Read 10:Min 0:Exit ");
scanf("%d", &choice);
switch(choice){
case 1:
head = Create_Stu_Doc();
break;
case 2:
printf("Input num,name and score: ");
scanf("%d%s%d", &num,name, &score);
p = (struct stud_node *) malloc(size);
p->num = num;
strcpy(p->name, name);
p->score = score;
head = InsertDoc(head, p);
break;
case 3:
printf("Input num: ");
scanf("%d", &num);
head = DeleteDoc(head, num);
break;
case 4:
Print_Stu_Doc(head);
break;
case 5:
printf("Input num: ");
scanf("%d", &num);
printf("Input score: ");
scanf("%d", &score);
head=Modify(head,num,score);
break;
case 6:
printf("Input num: ");
scanf("%d", &num);
p=Find(head,num);
if(p!=NULL)
printf("%d %s %d ", p->num, p->name, p->score);
else
printf("Not Found %d ",num);
break;
case 7:
p=Max(head);
if(p!=NULL)
printf("%d %s %d ", p->num, p->name, p->score);
else
printf("Not Found ");
break;
case 8:
Save(head);
break;
case 9:
head=Read();
break;
case 10:
p=Min(head);
if(p!=NULL)
printf("%d %s %d ", p->num, p->name, p->score);
else
printf("Not Found ");
break;
case 0:
break;
}
}while(choice != 0);

return 0;
}

/新建链表/
struct stud_node * Create_Stu_Doc()
{
struct stud_node * head,*p;
int num,score;
char name[20];
int size = sizeof(struct stud_node);

head = NULL;
printf("Input num,name and score:
");
scanf("%d%s%d", &num,name, &score);
while(num != 0){	/* 学号0表示输入结束，且学号0对应的姓名和成绩都要输入 */ 
   p = (struct stud_node *) malloc(size);
   p->num = num;
   strcpy(p->name, name);
   p->score = score;
   head = InsertDoc(head, p);    /* 调用插入函数 */
   scanf("%d%s%d", &num, name, &score);

}
return head;
}

/* 插入操作 */
struct stud_node * InsertDoc(struct stud_node * head, struct stud_node *stud)
{
struct stud_node ptr ,ptr1, *ptr2;

ptr2 = head; 
ptr = stud; 				/* ptr指向待插入的新的学生记录结点 */

if(head == NULL){ /* 原链表为空时的插入 */ 
    head = ptr; 			/* 新插入结点成为头结点 */
    head->next = NULL;
}
else{ 		      /* 原链表不为空时的插入 */
    while((ptr->num > ptr2->num) && (ptr2->next != NULL)){
        ptr1 = ptr2; 		/* ptr1, ptr2各后移一个结点 */
        ptr2 = ptr2->next;
    }
    if(ptr->num <= ptr2->num){ 	
        if(head == ptr2)  head = ptr;/* 新插入结点成为头结点 */
        else ptr1->next = ptr;		 /* 在ptr1与ptr2之间插入新结点 */
        ptr->next = ptr2;
    }
    else{						     /* 新插入结点成为尾结点 */
        ptr2->next = ptr;
        ptr->next = NULL; 
    } 
}
return head;

}

/* 删除操作 */
struct stud_node * DeleteDoc(struct stud_node * head, int num)
{
struct stud_node *ptr1, *ptr2;

if(head == NULL)  /*链表空 */
    return NULL;
else if(head->num == num){
    /* 要被删除结点为表头结点 */
    while(head != NULL && head->num == num){  
        ptr2 = head;
        head = head->next;
        free(ptr2);
    }
}
else{
	/* 要被删除结点为非表头结点  */
    ptr1 = head;
    ptr2 = head->next; /*从表头的下一个结点搜索所有符合删除要求的结点 */
    while(ptr2 != NULL){
        if(ptr2->num == num){ 	/* ptr2所指结点符合删除要求 */
            ptr1->next = ptr2->next;
            free(ptr2); 
        }
        else 
            ptr1 = ptr2;       /* ptr1后移一个结点 */
        ptr2 = ptr1->next;    /* ptr2指向ptr1的后一个结点 */
    }
}

return head;

}

/遍历操作/
void Print_Stu_Doc(struct stud_node * head)
{
struct stud_node * ptr;

if(head == NULL){
    printf("
No Records
");
    return;
}
printf("
The Students' Records Are: 
");
printf("Num	Name	Score
");
for(ptr = head; ptr != NULL; ptr = ptr->next)
  	printf("%d	%s	%d 
", ptr->num, ptr->name, ptr->score);

}

struct stud_node * Find(struct stud_node * head, int num) /查找/
{
struct stud_node *ptr;

if(head==NULL)
	return NULL;
else
{
	for(ptr=head;ptr!=NULL;ptr=ptr->next)/*for循环从head开始到NULL循环*/ 
		if(ptr->num==num)
			break;
			return ptr;
}

}

struct stud_node * Modify(struct stud_node * head, int num, int score)/修改通过查找学号修改成绩/
{
struct stud_node *ptr;

if(head==NULL)
	return NULL;
else
{
	for(ptr=head;ptr!=NULL;ptr=ptr->next)
		if(ptr->num==num)
		{
			ptr->score=score;
			break;
		}
				
	return head;
}

}

struct stud_node * Max(struct stud_node * head)
{
struct stud_node maxp,ptr;

if(head==NULL)
	return NULL;
else
{
	maxp=head;
	for(ptr=head->next;ptr!=NULL;ptr=ptr->next)
		if(maxp->score<ptr->score)
			maxp=ptr;
	
	return maxp;
}

}
struct stud_node * Min(struct stud_node * head)
{
struct stud_node minp,ptr;

if(head==NULL)
	return NULL;
else
{
	minp=head;
	for(ptr=head->next;ptr!=NULL;ptr=ptr->next)
		if(minp->score>ptr->score)
			minp=ptr;
	
	return minp;
}

}

void Save(struct stud_node * head)
{
FILE fp;
if((fp=fopen("data.txt","w")) == NULL){ /打开文件（套用）*/
printf("File open error! ");
exit(0);
}

struct stud_node * ptr;

if(head == NULL){
    return;
}

for(ptr = head; ptr->next != NULL; ptr = ptr->next)
  	fprintf(fp,"%d %s %d
", ptr->num, ptr->name, ptr->score);
fprintf(fp,"%d %s %d", ptr->num, ptr->name, ptr->score);/*输出的最后没有换行*/
	  
if( fclose(fp) ){/*关闭文件（套用）*/
	printf( "Can not close the file!
" );
	exit(0);
}	

}

struct stud_node *Read()
{
FILE *fp;
if((fp=fopen("data.txt","r")) == NULL){
printf("File open error! ");
exit(0);
}

struct stud_node * head,*tail,*p;
//int num,score;
//char  name[20];
int size = sizeof(struct stud_node);

head = tail=NULL;


while(!feof(fp)){	/* 读到结束标志结束 */ 
   p = (struct stud_node *) malloc(size);
   fscanf(fp,"%d%s%d", &p->num, p->name, &p->score);
   //head = InsertDoc(head, p);    /* 调用插入函数 */
   p->next = NULL;
	if(head == NULL) 
    	head = p;
	else  
    	tail->next = p;
	tail = p;  

}

	 if( fclose(fp) ){
	printf( "Can not close the file!
" );
	exit(0);
}

return head;

}