C语言链表的基本操作

#include<stdio.h>#include<stdlib.h>#include<conio.h>/*定义结构体*/struct student{int num;float score;struct student *next;};/*创建一个只有头结点的空链表*/struct student *create_head(){struct student *head;head=(struct student*)malloc(sizeof (struct student) );if(head==NULL)            {printf("申请头结点失败!\n");return NULL;}head->next=NULL;return head;}/*将s指向的结点插入链表,使链表保持升序,并返回头结点*/struct student *insert(struct student *head,struct student *s){struct student *p=head;while(p->next!=NULL&&s->score>p->next->score)//特别注意&&左右不能写反,若s最大,最后p->next=NULL,p->next->score运行出错p=p->next;if(p->next==NULL) //s->score最大的情况     //其实两种情况可以并在一块写{p->next=s;    //连接结点s->next=NULL;   //p->next就等于NULL}else {p->next=s;    //连接结点s->next=p->next;}return head ;}/*查找符合条件的结点,并返回指向该结点的指针*/struct student *search(struct student *head){struct student *p=head->next;int num;printf("请输入要查找学生的学号:\n");scanf("%d",&num);while(p!=NULL&&p->num!=num)   //特别注意两条件不能写反,若写反最后p指向NULL时p->num找不到 运行出错p=p->next;if(p==NULL)             //特别注意两个if不能调换,若调换最后p指向NULL时p->num运行出错{printf("找不到符合条件的结点!!!");return NULL;//查找不到返回空指针}if(p->num==num){printf("找到符合条件的结点\n该结点为%d\t%f",p->num,p->score);return p;//返回查找到的指针}}/*输出链表各结点的值,也称对链表的遍历*/void print(struct student *head){struct student *p;printf("  链表如下:  \n");p=head->next;while(p!=NULL){printf("%d\t%.1f\n",p->num,p->score);p=p->next;}}/*释放链表*/void free_list(struct student *head){struct student *p=head ;printf("释放链表:\n");while(p!=NULL){head=head->next;free(p);p=head;}printf("释放链表成功!\n");}/*删除链表中值为num的结点,并返回链表的首指针*/struct student *delete_note(struct student *head,int num_x){struct student *p1=head->next , *p2=head ;while(p1!=NULL&&p1->num!=num_x)  //特别注意&&左右条件不能调换,若调换如果p1指向NULL时p1->num运行出错{p2=p1;p1=p1->next;}if(p1==NULL)    //特别注意两个if不能调换,若调换如果p1指向NULL时,p1->num运行出错printf("找不到符合删除要求的结点!!!\n");if(p1->num==num_x){p2->next=p1->next;free(p1);printf("结点删除成功!\n");}return head;}/*完整的有头结点链表操作程序*/void main(){struct student *p , *head ;char c;int num ;float score ;printf("有头结点链表操作程序:\n");head=create_head();while(1){printf("I:插入结点(自动升序)  P:输出链表  S:查找结点  D:删除结点  E:释放链表并退出程序!  ");c=getch();switch(c){case'I':printf("请分别输入要插入学生的学号和分数:\n");scanf("%d%f",&num,&score);p=(struct student*)malloc( sizeof(struct student) );if(p==NULL){printf("申请该结点失败!!!\n");exit (0) ;}p->num=num;  p->score=score;   //给p赋值insert(head,p);printf("插入成功!\n");break;case'P':print(head);break;case'S':search(head);break;case'D':printf("请输入要删除的学生的学号:\n");scanf("%d",&num);delete_note(head,num);break;case'E':free_list(head);exit (0);}}}