对中国编程资格赛一题的解答

刚才看到一位朋友对中国编程资格赛中一个题目的解答，觉得答案略为复杂了一些。以下是我的解答，请大家指点：

原题：

Problem Statement

You are given a string input. You are to find the longest substring of input such that the reversal of the substring is also a substring of input. In case of a tie, return the string

that occurs earliest in input.
Definition

Class:
ReverseSubstring
Method:
findReversed
Parameters:
string
Returns:
string
Method signature:
string findReversed(string input)
(be sure your method is public)

Notes
-
The substring and its reversal may overlap partially or completely.
-
The entire original string is itself a valid substring (see example 4).
Constraints
-
input will contain between 1 and 50 characters, inclusive.
-
Each character of input will be an uppercase letter ('A'-'Z').
Examples
0)

"XBCDEFYWFEDCBZ"
Returns: "BCDEF"
We see that the reverse of BCDEF is FEDCB, which appears later in the string.
1)

"XYZ"
Returns: "X"
The best we can do is find a one character substring, so we implement the tie-breaker rule of taking the earliest one first.
2)

"ABCABA"
Returns: "ABA"
The string ABA is a palindrome (it's its own reversal), so it meets the criteria.
3)

"FDASJKUREKJFDFASIREYUFDHSAJYIREWQ"
Returns: "FDF"

4)

"ABCDCBA"
Returns: "ABCDCBA"
Here, the entire string is its own reversal.

解答：

 1public class ReverseSubstring
 2    {
 3        public string findReversed(string input)
 4        {
 5            int inputLen=input.Length;//input的长度
 6            string tmpStr;//临时substring
 7
 8            for (int tmpLen=inputLen;tmpLen>0;tmpLen--)//tmpLen表示临时substring的长度，从inputLen开始递减
 9            {
10                for (int start=0;start<=inputLen-tmpLen;start++)//start表示tmpStr的开始位置
11                {
12                    tmpStr=input.Substring(start,tmpLen);
13                    if (input.IndexOf(GetReversedStr(tmpStr))>=0)
14                    {
15                        return tmpStr;
16                    }
17                }
18            }
19            return "";
20        }
21
22        public static string GetReversedStr(string str)//Get 反序字符串
23        {
24            System.Text.StringBuilder ReversedStr=new System.Text.StringBuilder();
25            for (int i=0;i<str.Length;i++)
26            {
27                ReversedStr.Insert(0,str.Substring(i,1));
28            }
29            return ReversedStr.ToString();
30        }
31    }