/**

 * Definition for a binary tree node.

 * public class TreeNode {

 *     public int val;

 *     public TreeNode left;

 *     public TreeNode right;

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

 * }

 */

public class Solution {

    Queue<TreeNode> Q = new Queue<TreeNode>();

        private List<TreeNode> FloorSearch()

        {

            var floor = new List<TreeNode>();

            while (Q.Count > )

            {

                var node = Q.Dequeue();//出来一个节点，放入其左右子节点

                //将当前节点放入floor中

                floor.Add(node);

            }

            foreach (var f in floor)

            {

                if (f.left != null)

                {

                    Q.Enqueue(f.left);

                }

                if (f.right != null)

                {

                    Q.Enqueue(f.right);

                }

            }

            return floor;

        }

        public IList<int> LargestValues(TreeNode root)

        {

            var list = new List<int>();

            //层次遍历，每一层加入到一个list中，然后再从list中找最大的值

            if (root == null)

            {

                return new List<int>();

            }

            Q.Enqueue(root);

            var floor = new List<TreeNode>();

            do

            {

                floor = FloorSearch();

                if (floor.Count > )

                {

                    var max = floor.Max(x => x.val);

                    list.Add(max);

                }

            } while (floor.Count > );

            return list;

        }

}