c语言---链表

struct list
{
   int no;
   int score;
   struct list *next;            
};
//* listp为链表操作的当前节点，*p为新建节点，*listhead为链接头的指针
struct *p,*listp,*listhead;
//malloc分配size字节的内存，成功时返回一个指针，指向所分配的地址；失败后返回NULL
p=(struct list *)malloc(sizeof(struct list)); //申请一个新指针

listhead=p;//此次操作是首次创建新指针
listp=p;
listp->next=NULL;
listp->no=5
listp->score=86;

#include<stdio.h>
#include<stdlib.h>

struct list
{
    int no;
    int score;
    struct list *next;
 }; 
 
int main()
{
    int k;
    struct list *p,*listhead,*listp;
    for(k=1;k<=5;k++){
        p = (struct list*)malloc(sizeof(struct list));
        if(k==1){
            listhead=p;
        }
        else{
            listp->next=p;
        }
        listp = p;
        listp->next = NULL;
        printf("please input %d number and score:",k);
        scanf("%d %d",&listp->no,&listp->score);
    }

//打印输出各个节点 
    p = listhead;
    while(p!=NULL)
    {
        printf("%d student score is %d\n",p->no,p->score);
        p = p->next;
    }
        return 0;
    
    p = listhead;
//释放各个结点的内存空间
    while(p!=NULL){
        listp=p;
        p=p->next;
        free(listp);
    } 
}

#include<stdlib.h>
#include<stdio.h>

struct list{
    int data;
    struct list *next;
};

struct list *dele(struct list *head);
struct list *insert(struct list *head);
void display(struct list *head);
struct list * create();
struct list * deleall(struct list *listhead);

int main()
{
    int ch;
    struct list * head;
    head = NULL;
    
    while(1){
        printf("1.建立链表\n");
        printf("2.插入节点\n");
        printf("3.删除节点\n");
        printf("4.显示节点\n");
        printf("0.退出程序\n");
        scanf("%d",&ch);
        
        switch(ch){
            case 1:
                head = create();
                break;
            case 2:
                head = insert(head);
                break;
            case 3:
                head = dele(head);
                break;
            case 4:
                display(head);
                break;
            case 0:
                head = deleall(head);
        }
        if(ch == 0) break; 
    }
    
    return 0;
}
struct list *create(){
    struct list *listhead,*p,*listp;
    int x;
    listhead = NULL;
    printf("输入成绩：");
    scanf("%d",&x); 
    while(x!=-1){
        if((p=(struct list *)malloc(sizeof(struct list)))==NULL){
            printf("内存申请错误！");
            exit(0);
        }
        if(listhead == NULL){
            listhead = p;
        }
        else{
            listp->next=p;
        }
        listp=p;
        listp->data=x;
        listp->next=NULL;
        printf("请输入下一个值（-1结束输入）");
        scanf("%d",&x);
    }
    return listhead;
}

void display(struct list *listhead){
    struct list *p;
    if(listhead == NULL){
        printf("链表为空！\n");
        return ;
    }
    p = listhead;
    while(p!=NULL){
        printf("%d\n",p->data);
        p = p->next;
    } 

}

struct list *insert(struct list *listhead){
    struct list *p,*listp;
    int k,i,x;
    if(listhead==NULL){
        printf("链表还没有建立"); 
        return listhead;
    }
    printf("请输入需要插入的数据和w位置");
    scanf("%d %d",&x,&i);
    k = 1;
    listp=listhead;
    while(listp!=NULL&&k<i-1){
        listp=listp->next;
        k=k+1;
    }
    if(k<i-1||i<1){
        printf("无效插入点！\n");
    }
    else if(i==1){
        if((p=(struct list *)malloc(sizeof(struct list)))==NULL){
            printf("申请内存错误！");
            exit (0); 
        }
        p->data = x;
        p->next=listhead;
        listhead = p;
    }
    else{
        if((p=(struct list *)malloc(sizeof(struct list)))==NULL){
            printf("申请内存错误！");
            exit (0); 
        }
        p->data=x;
        p->next=listp->next;
        listp->next=p;
    }
    return listhead;
}

struct list *dele(struct list *listhead){
    struct list *listp,*p;
    int i,k;
    if(listhead == NULL){
        printf("次链表为空！");
        return listhead;
    }
    printf("请输入要删除的结点\n");
    scanf("%d",&i);
    k=1;
    listp=listhead;
    while(listp!=NULL&&k<i-1){
        listp=listp->next;
        k=k+1;
    }
    if(k<i-1 || i<1){
        printf("此节点为无效插入点\n");
    }
    else if(k==1){
        p=listhead;
        listhead=p->next;
        free(p);
    }
    else if (i>1 && k>=i-1){
        p =listp->next;
        listp->next=p->next;
        free(p);
    }
    return listhead;
}

struct list *deleall(struct list *listhead){
    struct list *p;
    p = listhead;
    while(p!=NULL){
        listhead=p->next;
        free(p);
        p=listhead;
    }
    return p;
}