C语言双向链表

　　今天写了点双向链表的各种操作，写插入的时候费了点时间，不过，现在看来还是值得耗费那点时间去写的，这种小东西应该能信手拈来才行啊。

/*双向链表*/
#include <stdio.h>
#include <string.h>    /*strcmp(const char *,const char *) return 0 is equal*/
 
 typedef struct dulnode
 {
    char name[20];
    struct dulnode *prior,*next;
 }stud;
 /*创建,返回链表头指针，参数n-节点个数*/
 stud * create(n);
 /*查找,返回节点地址，参数h-链表头指针，name为查询条件*/
 stud * search(stud *h,char *name);
 /*删除*/
 void del(stud *p);
 /*显示,参数-h,链表头节点，num-显示节点个数*/
 void show(stud *h,int num);
 /*求链表长度*/
 int length(stud *head);
 /*插入节点,参数head-链表头节点,name-节点，n-节点位置*/
 stud *insert(stud *head,char *name,int n); 
 int main()
 {
    stud *head,*re,*in;
    head = create(5);
    show(head,5);
    re = search(head,"Accipiter");
    show(re,1);
    del(re);
    re = head->next;
    show(re ,4);
    in = insert(re , "cnblogs",3);
    show(in,5);
    return 0;
 }
 void show(stud *head,int num)
 {
    stud *sp;
    int cnt = 1;
    if(NULL == head)
    {
        printf("It's NULL!\n");
        return;
    }
    if(num>length(head))
     {
        printf("It's Full\n");
        return ;
    }
    if(strcmp(head->name,"") == 0)
    {
        sp = head->next;
    }
    else
    {
        sp = head;
    }
    while(sp)
    {
        printf("name %d:%s\n",cnt,sp->name);
        if(cnt == num)
        {
            sp = NULL;
        }else
        {
            sp = sp->next;
            cnt++;
        }
    }
 }
 
stud * create(n)
{
    stud *p,*h,*s;/*p-前指针，h-头指针，s-后指针*/
    int i;
    /*构建头指针*/
    h = (stud *)malloc(sizeof(stud));
    if(h == NULL)
    {
        return NULL;
    }
    h->name[0] = '\0';
    h->prior = NULL;
    h->next = NULL;
    /*插入节点*/
    p = h;
    for(i=0;i<n;i++)
    {
        s = (stud *)malloc(sizeof(stud));
        if(NULL == s)
        {
            printf("node malloc error!\n");
            break;
        }
        p->next = s;
        printf("%d's name:\n",i+1);
        gets(s->name);
        s->prior = p;
        s->next = NULL;/*末尾插入*/
        p = s;
    }
    p->next = NULL;
    return (h);
}

stud * search(stud *head , char *name)
{
    stud *p,*re=NULL;
    p=head->next;
    while(p)
    {
        if(strcmp(p->name,name) == 0)
        {
            re = p;
            p = NULL;
        }
        else
        {
            p = p->next;
        }
    }
    if(re ==  NULL)
    {
        printf("Can't Find!\n");
    }
    return (re);
}

void del(stud *p)
{
    if(p == NULL|| (strcmp(p->name,"")==0))
    {
        printf("is Null or head!\n");
        return;
    }
    else
    {
        p->next->prior = p->prior;
        p->prior->next = p->next;
        free(p);
    }
}

int length(stud *head)
{
    int len=0;
    stud *sp;
    if(head != NULL)
    {
        len = 1;
        sp = head->next;
        while(sp)
        {
            sp = sp->next;
            len++;
        }    
    }
    return len;
}

stud *insert(stud *head , char *name , int n)
{
    stud *p,*nhead;
    int cnt=0;
    if(strcmp(head->name,"") != 0)
    {
        cnt=1;
    }
    nhead = head;
    if(n>length(head)||n<0)
    {
        printf("It's Full or Error!\n");
        return NULL;
    }
    /*插入节点*/
    while(cnt<n)
    {
        head = head->next;
        cnt++;
    }
    p = (stud *)malloc(sizeof(stud));
    if(p != NULL)
    {
         strcpy(p->name,name);
         p->next = head->next;
         p->prior = head;
    
         if(head->next)/*双向链表操作这里很重要*/
             head->next->prior=p;
            head->next=p;
    }
    
    return nhead;
}