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55 lines
1.4 KiB
Python
55 lines
1.4 KiB
Python
#!/usr/bin/env python
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# coding=utf-8
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###########################################################################
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# Leetcode 206 反转链表
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#
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# 反转一个单链表。
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#
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# 示例:
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# 输入: 1->2->3->4->5->NULL
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# 输出: 5->4->3->2->1->NULL
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#
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# 进阶:
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# 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？
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###########################################################################
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class ListNode:
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def __init__(self, x):
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self.val = x
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self.next = None
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def __repr__(self):
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if self:
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return "{}->{}".format(self.val, repr(self.next))
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class Solution:
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def reverseList(self, head):
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"""
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(knowledge)
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思路：
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1. 用两个指针，一个指针指向新链（初始为None），一个指向原链（初始为head）；
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2. 从头往后依次遍历，进行反挂；
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tip:跟着代码执行的流程，画个图，很快就能get到代码的实现思路了
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"""
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cur = None
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while head is not None:
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head.next, cur, head = cur, head, head.next
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return cur
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if __name__ == '__main__':
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head = ListNode(1)
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head.next = ListNode(2)
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head.next.next = ListNode(3)
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head.next.next.next = ListNode(4)
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head.next.next.next.next = ListNode(5)
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solution = Solution()
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print(solution.reverseList(head))
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