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題目要求

反轉(zhuǎn)一個(gè)單鏈表。

示例:
輸入: 1->2->3->4->5->NULL
輸出: 5->4->3->2->1->NULL

思路一

遍歷給定鏈表，摘下節(jié)點(diǎn)放到新鏈表，新鏈表從后向前構(gòu)造

→_→ talk is cheap, show me the code

# 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 not head:
            return None
        new = None
        while head:
            p = head
            head = head.next
            p.next = new
            new = p
        return new