LeetCode 206. 反转链表（C++、python）

反转一个单链表。

示例:

输入: 1->2->3->4->5->NULL
输出: 5->4->3->2->1->NULL

进阶:
你可以迭代或递归地反转链表。你能否用两种方法解决这道题？

C++

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* reverseList(ListNode* head) 
    {
        if(head==NULL || head->next==NULL)
        {
            return head;
        }
        ListNode* pcur=head,*pnext=NULL,*pnew=NULL;
        while(pcur)
        {
            pnext=pcur->next;
            pcur->next=pnew;
            pnew=pcur;
            pcur=pnext;            
        }
        return pnew;
        
    }
};

python

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    def reverseList(self, head):
        """
        :type head: ListNode
        :rtype: ListNode
        """
        if head==None or head.next==None:
            return head
        pcur=head
        pnew=None
        pnext=None
        while pcur:
            pnext=pcur.next
            pcur.next=pnew
            pnew=pcur
            pcur=pnext
        return pnew