138_copy_list_with_random_pointer

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

class Solution(object):
    def copyRandomList(self, head):
        """
        :type head: RandomListNode
        :rtype: RandomListNode
        """
        dic = dict()
        m = n = head
        while m:
            dic[m] = RandomListNode(m.label)
            m = m.next
        while n:
            dic[n].next = dic.get(n.next)
            dic[n].random = dic.get(n.random)
            n = n.next
        return dic.get(head)