C# 求最大相同子字符串

例如，abcdefg,xdefkl,那么最大相同子字符串为def

        static string LongCommonSubstring(string str1, string str2)
        {
            if (string.IsNullOrEmpty(str1) || string.IsNullOrEmpty(str2))
            {
                throw new Exception("input can't be empty.");
            }

            string result = "";
            int[,] strArr = new int[str1.Length, str2.Length];
            int max = 0;
            for (int i = 0; i < str1.Length; i++)
            {
                for (int j = 0; j < str2.Length; j++)
                {
                    strArr[i, j] = 0;
                    if (str1[i] == str2[j])
                    {
                        if (i - 1 >= 0 && j - 1 >= 0)
                        {
                            strArr[i, j] = strArr[i - 1, j - 1] + 1;
                        }
                        else
                        {
                            strArr[i, j] = 1;
                        }
                        if (max<strArr[i,j])
                        {
                            max = strArr[i,j];
                            result = str1.Substring(i-max+1, max);
                        }
                    }
                }
            }

            Print(strArr);

            return result;
        }

        static void Print(int[,] intArr)
        {
            for (int i = 0; i < intArr.GetLength(0); i++)
            {
                for (int j = 0; j < intArr.GetLength(1); j++)
                {
                    Console.Write(intArr[i,j]+",");
                }
                Console.WriteLine();
            }
        }