Copy List with Random Pointer

Problem

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.

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Idea

• 把每个节点复制一遍， 分别插到原节点后, 新节点的random也指向对应的新节点的random
• 把复制的节点弄成串然后分离出来

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Solution

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