/【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\n");
scanf("%d", &choice);
switch(choice){
case 1:
head = Create_Stu_Doc();
break;
case 2:
printf("Input num,name and score:\n");
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:\n");
scanf("%d", &num);
head = DeleteDoc(head, num);
break;
case 4:
Print_Stu_Doc(head);
break;
case 5:
printf("Input num:\n");
scanf("%d", &num);
printf("Input score:\n");
scanf("%d", &score);
head=Modify(head,num,score);
break;
case 6:
printf("Input num:\n");
scanf("%d", &num);
p=Find(head,num);
if(p!=NULL)
printf("%d\t%s\t%d \n", p->num, p->name, p->score);
else
printf("Not Found %d\n",num);
break;
case 7:
p=Max(head);
if(p!=NULL)
printf("%d\t%s\t%d \n", p->num, p->name, p->score);
else
printf("Not Found\n");
break;
case 8:
Save(head);
break;
case 9:
head=Read();
break;
case 10:
p=Min(head);
if(p!=NULL)
printf("%d\t%s\t%d \n", p->num, p->name, p->score);
else
printf("Not Found\n");
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:\n");
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("\nNo Records\n");return;
}
printf("\nThe Students' Records Are: \n");
printf("Num\tName\tScore\n");
for(ptr = head; ptr != NULL; ptr = ptr->next)printf("%d\t%s\t%d \n", 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!\n");
exit(0);
}

struct stud_node * ptr;if(head == NULL){return;
}for(ptr = head; ptr->next != NULL; ptr = ptr->next)fprintf(fp,"%d %s %d\n", 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!\n" );exit(0);
}   

}

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

}