参加Google™ Code Jam - 中国编程挑战赛(2)

编写了第二个题目，总分500，得分499.76分。估计这个计分还根据时间来的。时间越长得分越少。这次我先编译好直接copy的。
题目：
Problem Statement

A square matrix is a grid of NxN numbers. For example, the following is a 3x3 matrix:
4 3 5
2 4 5
0 1 9
One way to represent a matrix of numbers, each of which is between 0 and 9 inclusive, is as a row-major string. To generate the string, simply concatenate all of the elements from the first row followed by the second row and so on, without any spaces. For example, the above matrix would be represented as "435245019". You will be given a square matrix as a row-major string. Your task is to convert it into a string[], where each element represents one row of the original matrix. Element i of the string[] represents row i of the matrix. You should not include any spaces in your return. Hence, for the above string, you would return {"435","245","019"}. If the input does not represent a square matrix because the number of characters is not a perfect square, return an empty string[], {}.
Definition

Class:
MatrixTool
Method:
convert
Parameters:
string
Returns:
string[]
Method signature:
string[] convert(string s)
(be sure your method is public)

Constraints
-
s will contain between 1 and 50 digits, inclusive.
Examples
0)

"435245019"
Returns: {"435", "245", "019" }
The example above.
1)

"9"
Returns: {"9" }

2)

"0123456789"
Returns: { }
This input has 10 digits, and 10 is not a perfect square.
3)

"3357002966366183191503444273807479559869883303524"
Returns: {"3357002", "9663661", "8319150", "3444273", "8074795", "5986988", "3303524" }

我的代码：

public class MatrixTool
{
public MatrixTool()
{

}

public string[] convert(string s)
{
string[] returnValues;
//开平方
if (s.Length>50)
{
returnValues = new string[1]{"This input Length overflow."};
}
else
{
double d = System.Math.Sqrt((double)s.Length);
double di = System.Math.Ceiling(d);
if (d!=di)
{
returnValues = new string[1]{"This input has "+s.Length.ToString()+" digits, and "+s.Length.ToString()+" is not a perfect square."};
}
else
{
try
{
System.Convert.ToDouble(s);
}
catch
{
returnValues = new string[1]{"This input hasn't numbers."};
return returnValues;
}
int i = System.Convert.ToInt32(di);
int k=0;
//转换
returnValues = new string[i];
for (int j=0 ;j<i;j++)
{
returnValues[j] = s.Substring(k,i);
k = i*(j+1)-1;
}
}
}
return returnValues;
}

}