题目：

题解：

func copyRandomList(head *Node) *Node {
    if head == nil {
        return nil
    }
    for node := head; node != nil; node = node.Next.Next {
        node.Next = &Node{Val: node.Val, Next: node.Next}
    }
    for node := head; node != nil; node = node.Next.Next {
        if node.Random != nil {
            node.Next.Random = node.Random.Next
        }
    }
    headNew := head.Next
    for node := head; node != nil; node = node.Next {
        nodeNew := node.Next
        node.Next = node.Next.Next
        if nodeNew.Next != nil {
            nodeNew.Next = nodeNew.Next.Next
        }
    }
    return headNew
}