题源 https://leetcode-cn.com/problems/fu-za-lian-biao-de-fu-zhi-lcof/

Class RandomNode:
    def __init__(self,x:int,next:'RandomNode'=None,random:'RandomNode'=None):
        self.val=x
        self.next=next
        self.random=random
def copyRandomList(head:'RandomNode'):
    visited={}
    def dfs(root:'RandomNode'):
        if not root:
            return root
       	nonlocal visited
        if root in visited:
            return visited[root]
        copy=RandomNode(root.val)
        visited[root]=copy
        copy.next=dfs(root.next)
        copy.random=dfs(root.random)
        return copy
   	return dfs(head)