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

1490. Clone N-ary Tree

Level

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).

Follow up: Can your solution work for the graph problem?

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.

• Java
• C++
• Python
• Go

• /*
  // 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);
              newRoot.children.add(newChild);
          }
          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}
  }
  

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