A binary tree is given such that each node contains an additional random pointer which could point to any node in the tree or null.

Return adeep copyof the tree.

The tree is represented in the same input/output way as normal binary trees where each node is represented as a pair of[val, random_index]where:

• val: an integer representingNode.val
• random_index: the index of the node (in the input) where the random pointer points to, ornullif it does not point to any node.

You will be given the tree in classNodeand you should return the cloned tree in classNodeCopy.NodeCopyclass is just a clone ofNodeclass with the same attributes and constructors.

Example 1:

Input: root = [[1,null],null,[4,3],[7,0]]
Output: [[1,null],null,[4,3],[7,0]]
Explanation: The original binary tree is [1,null,4,7].
The random pointer of node one is null, so it is represented as [1, null].
The random pointer of node 4 is node 7, so it is represented as [4, 3] where 3 is the index of node 7 in the array representing the tree.
The random pointer of node 7 is node 1, so it is represented as [7, 0] where 0 is the index of node 1 in the array representing the tree.

Example 2:

Input: root = [[1,4],null,[1,0],null,[1,5],[1,5]]
Output: [[1,4],null,[1,0],null,[1,5],[1,5]]
Explanation: The random pointer of a node can be the node itself.

Example 3:

Input: root = [[1,6],[2,5],[3,4],[4,3],[5,2],[6,1],[7,0]]
Output: [[1,6],[2,5],[3,4],[4,3],[5,2],[6,1],[7,0]]

Example 4:

Input: root = []
Output: []

Example 5:

Input: root = [[1,null],null,[2,null],null,[1,null]]
Output: [[1,null],null,[2,null],null,[1,null]]

Constraints:

• The number of nodes in thetreeis in the range[0, 1000].
• Each node's value is between[1, 10^6].

這個題目跟[LeetCode] 133. Clone Graph_ Medium tag: BFS, DFS很像,只是資料結構不一樣,但是本質是一樣,都是利用一個dictionary去存node 和copynode, 利用DFS.

# Definition for Node.
# class Node:
#     def __init__(self, val=0, left=None, right=None, random=None):
#         self.val = val
#         self.left = left
#         self.right = right
#         self.random = random

class Solution:
    def copyRandomBinaryTree(self, root: 'Node') -> 'NodeCopy':
        visited = dict()
        return self.dfs(visited, root)
    
    
    def dfs(self, visited: dict, root: 'Node') -> 'NodeCopy':
        if not root: return
        if root in visited:
            return visited[root]
        copyRoot = NodeCopy(root.val)
        visited[root] = copyRoot
        copyRoot.left = self.dfs(visited, root.left)
        copyRoot.right = self.dfs(visited, root.right)
        copyRoot.random = self.dfs(visited, root.random)
        return copyRoot