(CareerCup)find the largest repetitive sequence

题目地址：http://www.careercup.com/question?id=5678716545925120

Given a string, find the largest repetitive sequence. Algo + Code 
Ex: abcdefbcd – bcd, banana – ana

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

namespace find_the_largest_repetitive_sequence
{
    class Program
    {
        static void Main(string[] args)
        {
            Do();
        }

        static void Do()
        {
            Console.WriteLine("please input a string : ");
            string input = Console.ReadLine();
            string result = Find(input);
            Console.WriteLine(string.Format("result : {0}", result));
            Do();
        }

        static string Find(string input)
        {
            //var array = input.ToCharArray();
            int subLength = input.Length - 1;
            while (subLength > 0)
            {
                for (int i = 0; i <= input.Length - subLength; i++)
                {
                    string tempResult = input.Substring(i, subLength);
                    for (int j = i + 1; j <= input.Length - subLength; j++)
                    {
                        string temp = input.Substring(j, subLength);
                        if (temp.Equals(tempResult, StringComparison.OrdinalIgnoreCase))
                        {
                            return temp;
                        }
                    }
                }
                subLength--;
            }
            return "";
        }
    }
}