Leetcode 331 - verify Preorder Serialization of a binary tree

Leetcode331_verifyPreorderSerializationofBinaryTree.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Leetcode331_VerifyPreorder
{
    class Program
    {
        /*
         * Leetcode 331:
         * leetcode Verify Preorder Serialization of a Binary Tree
         * 
         * In a binary tree, if we consider null as leaves, then

    all non-null node provides 2 outdegree and 1 indegree (2 children and 1 parent), except root
    all null node provides 0 outdegree and 1 indegree (0 child and 1 parent).
    Suppose we try to build this tree. During building, we record the difference between 
    out degree and in degree diff = outdegree - indegree. When the next node comes, we then 
    decrease diff by 1, because the node provides an in degree. If the node is not null, we 
    increase diff by2, because it provides two out degrees. If a serialization is correct, 
    diff should never be negative and diff will be zero when finished.

    from :https://leetcode.com/discuss/83824/7-lines-easy-java-solution
         */
        static void Main(string[] args)
        {
        }

        public static bool isValidSerialization(String preorder) {
            String[] nodes = preorder.Split(',');

            int outDegree = 1;    // indegree 
            foreach (String node in nodes) {
                outDegree--; 

                if (outDegree < 0) return false;
            
                if (!(node.CompareTo("#") == 0))
                {
                    outDegree += 2;
                }
            }

            return outDegree == 0;
        }
    }
}