Leetcode 300 - longest subsequence using binary search - pass online judge

Leetcode300_longestSubSequence_binarySearch.cs

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

namespace Leetcode300_LongestIncreasingSubsequence
{
    class Program
    {
        static void Main(string[] args)
        {
            var testcase = new int[] {10, 9, 2, 5, 3, 7, 101, 18 };

            var length = lengthOfLIS(testcase); 
        }

        /// <summary>
        /// Leetcode 300 
        /// problem statement 
        /// https://leetcode.com/problems/longest-increasing-subsequence/#/description
        /// discussion 
        /// https://discuss.leetcode.com/topic/28719/short-java-solution-using-dp-o-n-log-n/15
        /// 
        /// Read Array.BinarySearch document of C# 
        /// </summary>
        /// <param name="nums"></param>
        /// <returns></returns>
        public static int lengthOfLIS(int[] nums) {            
            var subSequence = new int[nums.Length]; // increasing subsequence

            int length = 0;

            foreach(var x in nums) {
                int position = Array.BinarySearch(subSequence, 0, length, x);

                // If the index is negative, it represents the bitwise
                // complement of the next larger element in the array.
                //
                if (position < 0)
                {
                    position = -(position + 1);
                }

                // this may be a replacement of existing number or add to the end
                subSequence[position] = x;

                // add a new number in the subSequence
                if (position == length) 
                {
                    length++;
                }
            }

            return length;
        }
    }
}