反转链表

给你单链表的头节点 head ，请你反转链表，并返回反转后的链表。
输入：head = [1,2,3,4,5]
输出：[5,4,3,2,1]

#反转链表

# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution(object):
    def reverseList(self, head):
        """
        :type head: ListNode
        :rtype: ListNode
        """
        #保存头结点
        tem=head
        newListNode=head
        stack=[]
        #放入栈中
        while (head!=None):
            stack.append(head.val)
            head=head.next
        #反转链表
        while (stack):    
            newListNode.val=stack.pop()
            newListNode=newListNode.next
        return tem