链表的就地逆置（递归+非递归）

#include 
#include 
typedef struct ListNode
{
    int v;
    struct ListNode * next;
}node;
node * add(node * head,int x)
{
    node * p = head;
    node * r = (node*)malloc(sizeof(node));
    r->next=NULL;
    r->v=x;
    if(!p)
        return r;
    while(p->next!=NULL)
    {
        p=p->next;
    }
    p->next=r;
    return head;
}
void print(node* head)
{
    node * p=head;
    while(p)
    {
        printf("%d\n",p->v);
        p=p->next;
    }
}
node * revers(node * head)
{
    node * p = head;
    if(!p)
        return NULL;
    p = head->next;
    head->next=NULL;
    while(p)
    {
        node * tmp = p->next;
        p->next=head;
        head = p;
        p = tmp;
    }
    return head;

}
void printl(node* head)
{
    if(!head)
        return;
    if(head->next)
        printl(head->next);
    printf("%d\n",head->v);
}
node * revc(node * head,node * old)
{
    if(!head)
        return head;
    if(!head->next)
    {
        head->next=old;
        return head;
    }
    if(head->next)
    {
        node * tmp = head->next;
        head->next=old;
        return revc(tmp,head);
    }

}
int main()
{
    node * head=NULL;
    for(int i=0;i<10;i++)
        head = add(head,i);
    print(head);
    head = revers(head);
    print(head);
    head =revc(head,NULL);
    print(head);
    return 0;
}

revers是非递归的，revc是递归的。