Largest values.. each level. Binary tree

LargestValues.java

package com.interviewbytes.trees;

import java.util.ArrayList;
import java.util.Deque;
import java.util.LinkedList;
import java.util.List;

public class LargestValues {


    public List<Integer> largestValues(TreeNode root) {

        List<Integer> list = new ArrayList<>();

        Deque<TreeNode> queue = new LinkedList<>();

        if (root != null) queue.offer(root);

        while (!queue.isEmpty()) {

            int size = queue.size();
            int max = Integer.MIN_VALUE;

            while (size > 0) {
                TreeNode node = queue.poll();
                max = Math.max(max, node.val);
                if (node.left != null) queue.offer(node.left);
                if (node.right != null) queue.offer(node.right);
                size--;
            }

            list.add(max);
        }


        return list;

    }
}

TreeNode.java

package com.interviewbytes.trees;

public class TreeNode {

    int val;
    TreeNode left;
    TreeNode right;

    TreeNode(int x) {
        val = x;
    }
}