Leetcode基础学习-Python2实现反转链表

反转链表

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？

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

class Solution(object):
    def reverseList(self, head):
        """
        :type head: ListNode
        :rtype: ListNode
        """
        if head == None:
            return head
        pre = head
        cur = head.next
        pre.next = None
        while cur:
            temp = cur.next
            cur.next = pre
            pre = cur
            cur = temp
        return pre




if __name__ == "__main__":
    head = ListNode(1)
    p1 = ListNode(2)
    p2 = ListNode(3)
    p3 = ListNode(4)
    p4 = ListNode(5)
    head.next = p1
    p1.next = p2
    p2.next = p3
    p3.next = p4
    p = Solution()
    p = p.reverseList(head)
    while p:
        print p.val
        p = p.next

运行截图