LeetCode 1490 Clone N-ary Tree

deep copy of a N-ary.

we met many problems like this: clone something(deep copy)

this is exactly the same with deep copy of a graph.

the core of this problem is: a very clear mind about what that hashmap do. and how to copy a new node with same node value and same children list.

class Solution {
    public Node cloneTree(Node root) {
        if (root == null) return null;
        
        LinkedList<Node> queue = new LinkedList<>();
        HashMap<Node, Node> visited = new HashMap<Node, Node>();
        
        queue.offer(root);
        visited.put(root, new Node(root.val, new ArrayList<>()));
        
        while (!queue.isEmpty()) {
            Node cur = queue.poll();
            int size = cur.children.size();
            for (int i = 0; i < size; i++) {
                
                //if (cur.children.get(i) != null) stack.push(cur.children.get(i));
                if (!visited.containsKey(cur.children.get(i))) {
                    visited.put(cur.children.get(i), new Node(cur.children.get(i).val, new ArrayList<>()));
                    queue.offer(cur.children.get(i));
                }
                visited.get(cur).children.add(visited.get(cur.children.get(i)));
            }
        }
        return visited.get(root);
    }
}