MaxLevelSumInBinaryTree

class GfG
{
	public static int maxLevelSum(Node root)
    {
        if(root == null)
            return 0;
            
        Queue<Node> q = new LinkedList<Node>();
        q.add(root);
        int sum = 0;
        int size = 0;
        int maxSum = Integer.MIN_VALUE;
        while(!q.isEmpty())
        {
            if(size == 0)
            {
                size = q.size();
                sum = 0;
            }
            while(size > 0)
            {
                Node temp = q.poll();
                sum += temp.data;
                if(temp.left != null)
                    q.add(temp.left);
                if(temp.right != null)
                    q.add(temp.right);
                size--;
            }
            maxSum = Math.max(maxSum, sum);
        }
        return maxSum;
    }
}