无头链表

#include<stdio.h>
#include<stdlib.h> 
typedef struct LINK
{
    int num;
    struct LINK *next;
    
}LINK,*pLINK;

int getNum()
{
    int num;
    printf("请输入数字：");
    scanf("%d",&num);
    return num;
}

pLINK headInsertData(pLINK head,pLINK *tail)
{
    if(head==NULL)
    {
        head=(pLINK)malloc(sizeof(LINK));
        head->num=getNum();
        head->next=NULL;
        *tail=head;
        return head;
    }
    pLINK p=(pLINK)malloc(sizeof(LINK));
    p->num=getNum();
    p->next=head;
    head=p;
    return head;
} 

pLINK tailInsertData(pLINK head,pLINK *tail)//尾插数据 
{
    if(head==NULL)
    {
        head=(pLINK)malloc(sizeof(LINK));
        head->num=getNum();
        head->next=NULL;
        *tail=head;
        return head;
    }
    pLINK temp;
    for(temp=head;temp->next!=NULL;temp=temp->next);
    pLINK p=(pLINK)malloc(sizeof(LINK));
    p->num=getNum();
    (*tail)->next=p; 
    p->next=NULL;
    *tail=p;
    return head;
}

pLINK headDeleteData(pLINK head,pLINK *tail)//头删数据 
{
    if(head==NULL)
    {
        printf("无信息可删\n");
        return NULL;
    }
    if(head->next==NULL)
    {
        free(head);
        head=NULL;
        *tail=NULL;
        return head;
    }
    pLINK p=head;
    head=head->next;
    free(p);
    p=NULL;
    return head;
    
}
pLINK tailDeleteData(pLINK head,pLINK *tail)//尾删数据 
{
    if(head==NULL)
    {
        printf("无信息可删\n");
        return NULL;
    }
        if(head->next==NULL)
    {
        free(head);
        head=NULL;
        *tail=NULL;
        return head;
    }
    pLINK temp;
    for(temp=head;temp->next!=*tail;temp=temp->next);
    free(*tail);
    *tail=temp;
    temp->next=NULL;
    return head;
}

void printData(pLINK head)//打印信息 
{
    if(head==NULL)
    {
        printf("无信息可打印\n");
        return;
        
    }
    pLINK temp;
    for(temp=head;temp!=NULL;temp=temp->next)
    {
        printf("[%d]-->",temp->num);
    }
    printf("NULL\n");
} 
int main()
{
    pLINK head=NULL;
    pLINK tail=NULL;
    int select;
    while (1)
    {
        printf("========\n");
        printf("1.头插文件\n");
        printf("2.尾插文件\n");
        printf("3.头删文件\n");             
        printf("4.尾删文件\n");
        printf("5.打印数据\n");
        printf("6.退出\n");               
        printf("========\n");       
        scanf("%d",&select);
        switch(select)
        {
            case 1:
                head=headInsertData(head,&tail);
                break;
            case 2:
                head=tailInsertData(head,&tail);
                break;
            case 3:
                head=headDeleteData(head,&tail);
                break;                              
            case 4:
                head=tailDeleteData(head,&tail);
                break;              
            case 5:
                printData(head);
                break;              
            case 6:
        
                return 0;   
            default:
                break;          
                
        }       
    }
}