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UPCOMING CHALLENGES:

Ruthenium 2019

CURRENT CHALLENGES:

Technetium 2019

PAST CHALLENGES

Molybdenum 2019

Niobium 2019

Zirconium 2019

Yttrium 2019

Strontium 2019

Rubidium 2018

Arsenicum 2018

Krypton 2018

Bromum 2018

Future Mobility

Grand Challenge

Digital Gold

Selenium 2018

Germanium 2018

Gallium 2018

Zinc 2018

Cuprum 2018

Cutting Complexity

Nickel 2018

Cobaltum 2018

Ferrum 2018

Manganum 2017

Chromium 2017

Vanadium 2016

Titanium 2016

Scandium 2016

Calcium 2015

Kalium 2015

Argon 2015

Chlorum 2014

Sulphur 2014

Phosphorus 2014

Silicium 2014

Aluminium 2014

Magnesium 2014

Natrium 2014

Neon 2014

Fluorum 2014

Oxygenium 2014

Nitrogenium 2013

Carbo 2013

Boron 2013

Beryllium 2013

Lithium 2013

Helium 2013

Hydrogenium 2013

Omega 2013

Psi 2012

Chi 2012

Phi 2012

Upsilon 2012

Tau 2012

Sigma 2012

Rho 2012

Pi 2012

Omicron 2012

Xi 2012

Nu 2011

Mu 2011

Lambda 2011

Kappa 2011

Iota 2011

Theta 2011

Eta 2011

Zeta 2011

Epsilon 2011

Delta 2011

Gamma 2011

Beta 2010

Alpha 2010

ambitious

Programming language:

A *prefix* of a string S is any leading contiguous part of S. A *suffix* of the string S is any trailing contiguous part of S. For example, "`c`" and "`cod`" are prefixes, and "`ty`" and "`ity`" are suffixes of the string "`codility`". For simplicity, we require prefixes and suffixes to be non-empty and shorter than the whole string S.

A *border* of a string S is any string that is both a prefix and a suffix. For example, "`cut`" is a border of a string "`cutletcut`", and a string "`barbararhubarb`" has two borders: "`b`" and "`barb`".

We are looking for such borders of S that have at least three non-overlapping occurrences; that is, for some string that occurs as a prefix, as a suffix and elsewhere in between. For example, for S = "`barbararhubarb`", the only such string is "`b`".

In this problem we consider only strings that consist of lower-case English letters (`a`−`z`).

Write a function:

class Solution { public int solution(String S); }

that, given a string S consisting of N characters, returns the length of its longest border that has at least three non-overlapping occurrences in the given string. If there is no such border in S, the function should return 0.

For example, given a string S as follows:

- if S = "
barbararhubarb" the function should return 1, as explained above;- if S = "
ababab" the function should return 2, as "ab" and "abab" are both borders of S, but only "ab" has three non-overlapping occurrences;- if S = "
baaab" the function should return 0, as its only border "b" occurs only twice.

Write an ** efficient** algorithm for the following assumptions:

- N is an integer within the range [0..1,000,000];
- string S consists only of lowercase letters (
a−z).

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