topcoder 題目250分（賦答案）

Problem Statement
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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
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Class:
ReverseSubstring
Method:
findReversed
Parameters:
String
Returns:
String
Method signature:
String findReversed(String input)
(be sure your method is public)
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Notes
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The substring and its reversal may overlap partially or completely.
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The entire original string is itself a valid substring (see example 4).
Constraints
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input will contain between 1 and 50 characters, inclusive.
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Each character of input will be an uppercase letter ('A'-'Z').
Examples
0)

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

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"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)

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

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"FDASJKUREKJFDFASIREYUFDHSAJYIREWQ"
Returns: "FDF"

4)

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