/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public List<Integer> largestValues(TreeNode root) {
        HashMap<Integer,Integer> maxValues = largestValuesHelper(root,0);
        if(maxValues==null)
            return new LinkedList<Integer>();
        LinkedList<Integer> out = new LinkedList<Integer>();
        for(int i = 0; i<maxValues.size();i++){
            out.add(maxValues.get(i));
        }
        return out;
    }
    public HashMap<Integer,Integer> largestValuesHelper(TreeNode node,int row){
        HashMap<Integer, Integer> maxRight = new HashMap<Integer, Integer>(),
                                  max=new HashMap<Integer,Integer>();
        if(node==null){
            return null;
        }
        if(node.left!=null){
            max=largestValuesHelper(node.left,row+1);
        }
        if(node.right!=null){
            maxRight=largestValuesHelper(node.right,row+1);
        }
        max.put(row,node.val);
        for(Integer level:maxRight.keySet()){
            max.put(level,Math.max(maxRight.get(level),max.getOrDefault(level,Integer.MIN_VALUE)));
        }
        return max;
    }
}