ReverseSubstring | Topcoder Archive

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

```
"XBCDEFYWFEDCBZ"
```
```
Returns: "BCDEF"
```
We see that the reverse of BCDEF is FEDCB, which appears later in the string.
```
"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.
```
"ABCABA"
```
```
Returns: "ABA"
```
The string ABA is a palindrome (it's its own reversal), so it meets the criteria.

"FDASJKUREKJFDFASIREYUFDHSAJYIREWQ"

Returns: "FDF"

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

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