剑指offer 复杂链表的复制

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复杂链表的复制

题目

Leetcode 138.复制带随机指针的链表

输入一个复杂链表（每个节点中有节点值，以及两个指针，一个指向下一个节点，另一个特殊指针指向任意一个节点），返回结果为复制后复杂链表的head。（注意，输出结果中请不要返回参数中的节点引用，否则判题程序会直接返回空）

方法

方法1：不采用字典

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# -*- coding:utf-8 -*-
# class RandomListNode:
#     def __init__(self, x):
#         self.label = x
#         self.next = None
#         self.random = None
class Solution:
    # 返回 RandomListNode
    def Clone(self, pHead):
        # write code here
        if not pHead:
            return

        pre=pHead
        while pre:
            tmp=pre.next
            pre.next=RandomListNode(pre.label)
            pre.next.next=tmp
            pre=pre.next.next

        pre=pHead
        while pre:
            if pre.random:
                pre.next.random=pre.random.next
            pre=pre.next.next

        res=pHead.next
        cur=res
        pre=pHead
        while pre:
            pre.next=pre.next.next      # 如果pre.next.next是None
            if cur.next:                
                cur.next=cur.next.next
            pre=pre.next
            cur=cur.next
        return res

修改最后一部分：拆分新旧链表。这比较容易理解

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# -*- coding:utf-8 -*-
# class RandomListNode:
#     def __init__(self, x):
#         self.label = x
#         self.next = None
#         self.random = None
class Solution:
    # 返回 RandomListNode
    def Clone(self, pHead):
        # write code here
        if not pHead:
            return
        pre=pHead
        while pre:
            tmp=pre.next
            pre.next=RandomListNode(pre.label)
            pre.next.next=tmp
            pre=pre.next.next

        pre=pHead
        while pre:
            if pre.random:
                pre.next.random=pre.random.next
            pre=pre.next.next

        pre=pHead
        res=pHead.next
        cur=res
        while cur.next:
            pre.next=cur.next
            pre=pre.next

            cur.next=pre.next
            cur=cur.next
        pre.next=None
        cur.next=None
        return res
```            


#### 方法2：采用字典
```python
# -*- coding:utf-8 -*-
# class RandomListNode:
#     def __init__(self, x):
#         self.label = x
#         self.next = None
#         self.random = None
class Solution:
    # 返回 RandomListNode
    def Clone(self, pHead):
        # write code here
        if not pHead:
            return pHead
        copy = RandomListNode(pHead.label)
        dic = {pHead: copy}
        while pHead:
            tcopy = dic[pHead]
            if pHead.next:                  # 只有当pHead.next不为空才有后续操作
                if pHead.next not in dic:
                    dic[pHead.next] = RandomListNode(pHead.next.label)
                tcopy.next = dic[pHead.next]
            if pHead.random:
                if pHead.random not in dic:
                    dic[pHead.random] = RandomListNode(pHead.random.label)
                tcopy.random = dic[pHead.random]
            pHead = pHead.next
        return copy