Leetcode 516 - longest palindromic subsequence - pass online judge

Leetcode516_longestPalindromicSubsequence.cs

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

namespace Leetcode516_longestPalindromicSubsequence
{
    /// <summary>
    /// Leetcode 516: longest palindromic subsequence 
    /// https://leetcode.com/problems/longest-palindromic-subsequence/#/description
    /// </summary>
    class Program
    {
        static void Main(string[] args)
        {
            var test = "abbccdbda";
            int length = longestPalindromeSubseq(test); 
        }

        public static  int longestPalindromeSubseq(String s) {
            if( s == null || s.Length == 0)
            {
                return 0; 
            }

            int length = s.Length; 

            var subsequence = new int[length][];
            for (int i = 0; i < length; i++)
            {
                subsequence[i] = new int[length]; 
            }

            // assuming i < j, subsequence from index i to index j
            for (int i = length - 1; i >= 0; i--)
            {
                subsequence[i][i] = 1;

                for (int j = i + 1; j < length; j++)
                {
                    if (s[i] == s[j])
                    {
                        subsequence[i][j] = subsequence[i + 1][j - 1] + 2;
                    }
                    else
                    {
                        subsequence[i][j] = Math.Max(subsequence[i + 1][j], subsequence[i][j - 1]);
                    }
                }
            }

            return subsequence[0][length - 1];
        }
    }
}