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<int> values = new List<int>();
  int goodNodes = 0;
  bool badNode = false;

  public int GoodNodes(TreeNode root) {
    if (root == null)
      return goodNodes;
    for (int i = 0; i < values.Count; i++)
      if (root.val < values[i])
        badNode = true;
    if (!badNode)
      goodNodes++;
    else
      badNode = false;
    /* store val in path list */
    values.Add(root.val);
    GoodNodes(root.left);
    GoodNodes(root.right);
    /* done processing, erase the node from comp list */
    values.RemoveAt(values.Count - 1);

    return goodNodes;         
  }
}