LeetCode 206. 反转链表

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */


struct ListNode* reverseList(struct ListNode* head){
    if(head==NULL)
        return;
    int len,i,j,temp;
    struct ListNode *p=head;
    for(len=0;p->next!=NULL;len++)
        p=p->next;
    j=len;
    for(i=len;i!=0;i--){
        p=head;
        for(j=0;j<i;j++){
            temp=p->val;
            p->val=p->next->val;
            p->next->val=temp;
            p=p->next;
        }
    }
    return head;
}

struct ListNode* reverseList(struct ListNode* head)
{
    if(head==NULL)
      return NULL;
    struct ListNode *h1,*h2,*h3;
    h1=NULL;
    h2=head;
    h3=head->next;
    while(h2!=NULL)
    {
        h2->next=h1;
        h1=h2;
        h2=h3;
        h3=h2->next;
    }
    return h2;
}