You need to find the largest value in each row of a binary tree.

Example:

Input:


          1
         / \
        3   2
       / \   \  
      5   3   9 


Output:
 [1, 3, 9]

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public class Solution {
    public List<Integer> largestValues(TreeNode root) {
        List<Integer> res = new ArrayList<>();
        if (root == null) return res;

        Queue<TreeNode> queue = new LinkedList<>();
        queue.add(root);

        while (!queue.isEmpty()) {
            int size = queue.size();
            int max = Integer.MIN_VALUE;
            for (int i = 0; i < size; i++) {
                TreeNode node = queue.poll();
                max = Math.max(max, node.val);
                if (node.left != null) queue.add(node.left);
                if (node.right != null) queue.add(node.right);
            }
            res.add(max);
        }
        return res;
    }
}