138. Copy List with Random Pointer

A linked list is given such that each node contains an additional random pointer which could point to any node in the list or null.

Return a deep copy of the list. 这题 是靠http://www.cnblogs.com/zuoyuan/p/3745126.html 的写的，主要思想是在node后面插入当前node 然后 再用tmp从头开始读

tmp.next.random = tmp.random.next

最后再把链表重新拆分成两个。

代码如下：

# Definition for singly-linked list with a random pointer.
# class RandomListNode:
#     def __init__(self, x):
#         self.label = x
#         self.next = None
#         self.random = None

class Solution:
    # @param head, a RandomListNode
    # @return a RandomListNode
    def copyRandomList(self, head):
        if head==None:
            return head
        tmp=head
        while tmp:
            node=RandomListNode(tmp.label)
            node.next=tmp.next
            tmp.next=node
            tmp=tmp.next.next## jump 2 nodes
        tmp=head
        while tmp:## to make sure all the nodes are covered
            if tmp.random:
                tmp.next.random=tmp.random.next## this step is most important
            tmp=tmp.next.next ## jump 2 nodes
        oldh=head
        newhead=newh=head.next
        while newh.next:
            oldh.next=newh.next
            oldh=oldh.next
            newh.next=oldh.next
            newh=newh.next
        oldh.next=None
        newh.next=None
        return newhead