RepeatStringEasy | Topcoder Archive

Problem Statement

A string S is called a square if there is some string T such that S = T + T. For example, the strings "", aabaab" and "xxxx" are squares, but "a", "aabb" and "aabbaa" are not.

You are given a String s. Find the longest square string that can be obtained from s by erasing some (possibly none, possibly all) of its characters. In other words, we are looking for the longest square that occurs in s as a subsequence. Return the length of that square.

Note that the answer is well-defined, as the square "" (the empty string) will always occur in s as a subsequence.

Definition

Class:: RepeatStringEasy
Method:: maximalLength
Parameters:: String
Returns:: int
Method signature:: int maximalLength(String s)
(be sure your method is public)

Constraints

s will contain between 1 and 50 characters, inclusive.
Each character in s will be a lowercase English letter ('a'-'z').

Examples

```
"frankfurt"
```
```
Returns: 4
```
The longest square that occurs in "frankfurt" is "frfr". Its length is 4.
```
"single"
```
```
Returns: 0
```
The letters in the string "single" are all distinct. Hence, the only square that occurs in this string is "". The length of this square is zero.
```
"singing"
```
```
Returns: 6
```
```
"aababbababbabbbbabbabb"
```
```
Returns: 18
```
```
"x"
```
```
Returns: 0
```

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