单链表翻转与逆向遍历

#include<stdio.h>

typedef struct link
{
    int data;
    struct link *next;
}node;

int isCircle(node *head)
{
    node *p=head,*q=head;
    while(p->next && q->next)
    {
        p=p->next;
        if(NULL==(q=q->next->next))
            return 0;
        if(p==q)
          return 1;
    }
    return 0;
}

node *create()
{
    node *head,*p,*s;
    int x,cycle=1;
    head=(node *)malloc(sizeof(node));
    p=head;
    printf("please input the data (end with zero):\n");
    while(cycle)
    {
        scanf("%d",&x);
        if(x!=0)
        {
            s=(node *)malloc(sizeof(node));
            s->data=x;
            p->next=s;
            p=s;
        }
        else
          cycle=0;
    }
    head=head->next; /* 删除头结点 */
    p->next=NULL;
    printf("\nhead = %d\n",head->data);
    return (head);
}

void display(node *head)
{
    node *p;
    int n=0;
    p=head;
    while(p!=NULL)
    {
        p=p->next;
        n++;
    }
    printf("\nNow,These %d recodes are :\n",n);
    p=head;
    if(head!=NULL)
      while(p)
      {
          printf(" %d -> ",p->data);
          p=p->next;
      }
    printf("\n");
}

node *reverse(node *head)
{
    /* p1 -> p2 -> p3 先让p2逆置：
       p1 <- p2 -> p3 然后p1,p2向后推进：
       xx <- p1 -> p2 -> p3 重复进行直到p2为空。
    */
    node *p1,*p2,*p3;

    if(head == NULL || head->next == NULL)
        return head;

    /* p1=head, p2=p1->next; This is OK. */
    p1=head;
    p2=p1->next;
    p1->next=NULL;
    while(p2)
    {
        p3=p2->next;
        p2->next=p1;
        p1=p2;
        p2=p3;
    }

    head->next = NULL;
    head = p1;
    return head;
}

main()
{
    node *head;
    head = create();
    /* display(head); */
    head = reverse(head);
    display(head);

}

从尾到头遍历单链表：

void rvs_visit(node* head)
{
    if(head != NULL)
    {
        if(head->next != NULL)    //visit the next node first
        {
            rvs_visit(head->next);
        }
        printf("%d <-", head->data);
    }
}