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:

Image text

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

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

Example 2:

Image text

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);
            newRoot.children.add(newChild);
        }
        return newRoot;
    }
}

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