CODE

/**
* Definition for a binary tree node.
* public class TreeNode {
*     public int val;
*     public TreeNode left;
*     public TreeNode right;
*     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
*         this.val = val;
*         this.left = left;
*         this.right = right;
*     }
* }
*/

public class Solution {
  List<TreeNode> lvl = new List<TreeNode>();
  List<TreeNode> lvl2 = new List<TreeNode>(); 
  List<List<TreeNode>> lot = new List<List<TreeNode>>();
  List<List<int>> lotV = new List<List<int>>();  
  List<int> result = new List<int>();

  public List<int> RightSideView(TreeNode root) {

    if (root == null)
      return result;
    if (lot.Count == 0) {
      lvl.Add(root);
      lot.Add(lvl);
    }
    int j = 0;
    while (j < lot.Count)
    {
      List<int> lvl2V = new List<int>();               
      foreach (var v in lvl)
      {
        lvl2.Add(v);
        lvl2V.Add(v.val);
      }
      lotV.Add(lvl2V);

      lvl.Clear();
      while(lvl2.Count > 0)
      {
        if (lvl2[0].left != null)
          lvl.Add(lvl2[0].left);
        if (lvl2[0].right != null)
          lvl.Add(lvl2[0].right);
        lvl2.RemoveAt(0);
      }
      if (lvl.Count > 0)
        lot.Add(lvl);
      lvl2.Clear();
      j++;
    }
    for (int i = 0; i < lotV.Count; i++)
      result.Add(lotV[i][lotV[i].Count-1]);
    return result;
  }
}