104_Maximum_Depth_of_Binary_Tree.cs

/**
 * 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 {
    public int MaxDepth(TreeNode root) {
        if (root == null){
            return 0;
        }
        
        if (root.left == null && root.right == null){
            return 1;
        }
        
        return 1 + Math.Max(MaxDepth(root.left), MaxDepth(root.right));
    }
}