LeetCode 138. Copy List with Random Pointer [Python]_怎么理解copy list with random pointer medium python-优快云博客

本文链接：https://blog.youkuaiyun.com/yfeng18/article/details/103760338

本文介绍了一种解决LeetCode上复杂链表复制问题的方法，该链表节点包含一个额外的随机指针。通过使用哈希表，文章详细阐述了如何创建链表的深拷贝，包括两步：首先复制所有节点到哈希表，然后根据原始链表建立关系。

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LeetCode link: https://leetcode.com/problems/copy-list-with-random-pointer/

Question Description:

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.
The Linked List is represented in the input/output as a list of n nodes. Each node is represented as a pair of [val, random_index] where:

val: an integer representing Node.val
random_index: the index of the node (range from 0 to n-1) where random pointer points to, or null if it does not point to any node.

Method:

Create hash table, copy every node to hash table.
Build relationship according to original linked list.

Code:

class Solution:
    def copyRandomList(self, head: 'Node') -> 'Node':
        if head is None:
            return None
        
        nodeDict = dict()
        
        # First loop to copy all node
        pointer = head
        while pointer:
            nodeDict[pointer] = Node(pointer.val, None, None)
            pointer = pointer.next
        
        # Second loop to copy relationship
        pointer = head
        while pointer:
            if pointer.next:
                nodeDict[pointer].next = nodeDict[pointer.next]
            if pointer.random:
                nodeDict[pointer].random = nodeDict[pointer.random]
            pointer = pointer.next
        
        return nodeDict[head]