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Formatted question description: https://leetcode.ca/all/1490.html

# 1490. Clone N-ary Tree

Medium

## Description

Given a root of an N-ary tree, return a deep copy (clone) of the tree.

Each node in the n-ary tree contains a val (int) and a list (List[Node]) of its children.

class Node {
public int val;
public List<Node> children;
}


Nary-Tree input serialization is represented in their level order traversal, each group of children is separated by the null value (See examples).

Example 1:

Input: root = [1,null,3,2,4,null,5,6]

Output: [1,null,3,2,4,null,5,6]

Example 2:

Input: root = [1,null,2,3,4,5,null,null,6,7,null,8,null,9,10,null,null,11,null,12,null,13,null,null,14]

Output: [1,null,2,3,4,5,null,null,6,7,null,8,null,9,10,null,null,11,null,12,null,13,null,null,14]

Constraints:

• The depth of the n-ary tree is less than or equal to 1000.
• The total number of nodes is between [0, 10^4].

## Solution

Use recursion to do the cloning. If root is null, then return null. Otherwise, clone a new root from root, and do the cloning for each child of root and assign the cloned children to the new root. Finally, return the new root.

• /*
// Definition for a Node.
class Node {
public int val;
public List<Node> children;

public Node() {
children = new ArrayList<Node>();
}

public Node(int _val) {
val = _val;
children = new ArrayList<Node>();
}

public Node(int _val,ArrayList<Node> _children) {
val = _val;
children = _children;
}
};
*/

class Solution {
public Node cloneTree(Node root) {
if (root == null)
return root;
Node newRoot = new Node(root.val);
List<Node> children = root.children;
for (Node child : children) {
Node newChild = cloneTree(child);
}
return newRoot;
}
}

• // OJ: https://leetcode.com/problems/clone-n-ary-tree/
// Time: O(N)
// Space: O(H)
class Solution {
public:
Node* cloneTree(Node* root) {
if (!root) return nullptr;
auto cpy = new Node(root->val);
for (auto &c : root->children) cpy->children.push_back(cloneTree(c));
return cpy;
}
};

• """
# Definition for a Node.
class Node:
def __init__(self, val=None, children=None):
self.val = val
self.children = children if children is not None else []
"""

class Solution:
def cloneTree(self, root: 'Node') -> 'Node':
if root:
node = Node(val=root.val)
node.children = [self.cloneTree(child) for child in root.children]
return node


• /**
* Definition for a Node.
* type Node struct {
*     Val int
*     Children []*Node
* }
*/

func cloneTree(root *Node) *Node {
if root == nil {
return nil
}
children := []*Node{}
for _, child := range root.Children {
children = append(children, cloneTree(child))
}
return &Node{root.Val, children}
}