1448.GoodNodes.cs

// 1448. Count Good Nodes in Binary Tree
// Given a binary tree root, a node X in the tree is named good if in the path from root to X there are no nodes with a value greater than X.
// Return the number of good nodes in the binary tree.
// Example 1:
// Input: root = [3,1,4,3,null,1,5]
// Output: 4
// Explanation: Nodes in blue are good.
// Root Node (3) is always a good node.
// Node 4 -> (3,4) is the maximum value in the path starting from the root.
// Node 5 -> (3,4,5) is the maximum value in the path
// Node 3 -> (3,1,3) is the maximum value in the path.
// Example 2:
// Input: root = [3,3,null,4,2]
// Output: 3
// Explanation: Node 2 -> (3, 3, 2) is not good, because "3" is higher than it.
// Example 3:
// Input: root = [1]
// Output: 1
// Explanation: Root is considered as good.

/**
 * 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 {
    public int GoodNodes(TreeNode root) {
        return 1 + Traverse(root.left,root.val) +Traverse(root.right,root.val);
    }
    
    public int Traverse(TreeNode root, int max){
        if(root == null)
            return 0;
        if(max > root.val){
            return Traverse(root.left,max) +Traverse(root.right,max);
        }
        return 1 + Traverse(root.left,root.val) +Traverse(root.right,root.val);
    }
}