CTCI 4.4

Given a binary tree, design an algorithm which creates a linked list of all the nodes at each depth(e.g., if you have a tree with depth D, you'll have D linked lists).

CTCI 4.4.java

public static ArrayList<LinkedList<Node>> createNodeLists(Node root){
    
    ArrayList<LinkedList<Node>> nodeLists = new ArrayList<LinkedList<Node>>();
    LinkedList<Node> thisList = new LinkedList<Node>();
    if(root != null) thisList.add(root);
    
    while(!thisList.isempty()){
        nodeLists.add(thisList);
        LinkedList<Node> sons = new LinkedList<Node>();
        for(Node n: thisList){
            if(n.left != null) sons.add(n.left);
            if(n.right != null) sons.add(n.right);
        }
        thisList = sons;
    }
    
    return nodeLists;
}