leetcode515

/**
 * 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 > 0)
            {
                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 > 0)
                {
                    var max = floor.Max(x => x.val);
                    list.Add(max);
                }
            } while (floor.Count > 0);

            return list;
        }
}

https://leetcode.com/problems/find-largest-value-in-each-tree-row/#/description