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Given a string S, find the length of the longest balanced substring of S.

Programming language:
Spoken language:

A string is *balanced* if it consists of exactly two different characters and both of those characters appear exactly the same number of times. For example: "aabbab" is balanced (both 'a' and 'b' occur three times) but "aabba" is not balanced ('a' occurs three times, 'b' occurs two times). String "aabbcc" is also not balanced (it contains three different letters).

A *substring* of string S is a string that consists of consecutive letters in S. For example: "ompu" is a substring of "c** ompu**ter" but "cmptr" is not.

Write a function `solution` that, given a string S, returns the length of the longest balanced substring of S.

**Examples:**

1. Given S = "cabbacc", the function should return 4 ("abba" is the longest balanced substring).

2. Given S = "abababa", the function should return 6 ("ababab" and "bababa" are the longest balanced substrings).

3. Given S = "aaaaaaa", the function should return 0 (S does not contain a balanced substring).

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

- N is an integer within the range [1..100,000];
- string S consists only of lowercase letters (
a−z).

Copyright 2009–2018 by Codility Limited. All Rights Reserved. Unauthorized copying, publication or disclosure prohibited.

A string is *balanced* if it consists of exactly two different characters and both of those characters appear exactly the same number of times. For example: "aabbab" is balanced (both 'a' and 'b' occur three times) but "aabba" is not balanced ('a' occurs three times, 'b' occurs two times). String "aabbcc" is also not balanced (it contains three different letters).

A *substring* of string S is a string that consists of consecutive letters in S. For example: "ompu" is a substring of "c** ompu**ter" but "cmptr" is not.

Write a function `solution` that, given a string S, returns the length of the longest balanced substring of S.

**Examples:**

1. Given S = "cabbacc", the function should return 4 ("abba" is the longest balanced substring).

2. Given S = "abababa", the function should return 6 ("ababab" and "bababa" are the longest balanced substrings).

3. Given S = "aaaaaaa", the function should return 0 (S does not contain a balanced substring).

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

- N is an integer within the range [1..100,000];
- string S consists only of lowercase letters (
a−z).

Copyright 2009–2018 by Codility Limited. All Rights Reserved. Unauthorized copying, publication or disclosure prohibited.

A string is *balanced* if it consists of exactly two different characters and both of those characters appear exactly the same number of times. For example: "aabbab" is balanced (both 'a' and 'b' occur three times) but "aabba" is not balanced ('a' occurs three times, 'b' occurs two times). String "aabbcc" is also not balanced (it contains three different letters).

A *substring* of string S is a string that consists of consecutive letters in S. For example: "ompu" is a substring of "c** ompu**ter" but "cmptr" is not.

Write a function `solution` that, given a string S, returns the length of the longest balanced substring of S.

**Examples:**

1. Given S = "cabbacc", the function should return 4 ("abba" is the longest balanced substring).

2. Given S = "abababa", the function should return 6 ("ababab" and "bababa" are the longest balanced substrings).

3. Given S = "aaaaaaa", the function should return 0 (S does not contain a balanced substring).

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

- N is an integer within the range [1..100,000];
- string S consists only of lowercase letters (
a−z).

Copyright 2009–2018 by Codility Limited. All Rights Reserved. Unauthorized copying, publication or disclosure prohibited.

*balanced* if it consists of exactly two different characters and both of those characters appear exactly the same number of times. For example: "aabbab" is balanced (both 'a' and 'b' occur three times) but "aabba" is not balanced ('a' occurs three times, 'b' occurs two times). String "aabbcc" is also not balanced (it contains three different letters).

*substring* of string S is a string that consists of consecutive letters in S. For example: "ompu" is a substring of "c** ompu**ter" but "cmptr" is not.

Write a function `Solution` that, given a string S, returns the length of the longest balanced substring of S.

**Examples:**

1. Given S = "cabbacc", the function should return 4 ("abba" is the longest balanced substring).

3. Given S = "aaaaaaa", the function should return 0 (S does not contain a balanced substring).

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

- N is an integer within the range [1..100,000];
- string S consists only of lowercase letters (
a−z).

*balanced* if it consists of exactly two different characters and both of those characters appear exactly the same number of times. For example: "aabbab" is balanced (both 'a' and 'b' occur three times) but "aabba" is not balanced ('a' occurs three times, 'b' occurs two times). String "aabbcc" is also not balanced (it contains three different letters).

*substring* of string S is a string that consists of consecutive letters in S. For example: "ompu" is a substring of "c** ompu**ter" but "cmptr" is not.

`solution` that, given a string S, returns the length of the longest balanced substring of S.

**Examples:**

1. Given S = "cabbacc", the function should return 4 ("abba" is the longest balanced substring).

3. Given S = "aaaaaaa", the function should return 0 (S does not contain a balanced substring).

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

- N is an integer within the range [1..100,000];
- string S consists only of lowercase letters (
a−z).

*balanced* if it consists of exactly two different characters and both of those characters appear exactly the same number of times. For example: "aabbab" is balanced (both 'a' and 'b' occur three times) but "aabba" is not balanced ('a' occurs three times, 'b' occurs two times). String "aabbcc" is also not balanced (it contains three different letters).

*substring* of string S is a string that consists of consecutive letters in S. For example: "ompu" is a substring of "c** ompu**ter" but "cmptr" is not.

`solution` that, given a string S, returns the length of the longest balanced substring of S.

**Examples:**

1. Given S = "cabbacc", the function should return 4 ("abba" is the longest balanced substring).

3. Given S = "aaaaaaa", the function should return 0 (S does not contain a balanced substring).

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

- N is an integer within the range [1..100,000];
- string S consists only of lowercase letters (
a−z).

*balanced* if it consists of exactly two different characters and both of those characters appear exactly the same number of times. For example: "aabbab" is balanced (both 'a' and 'b' occur three times) but "aabba" is not balanced ('a' occurs three times, 'b' occurs two times). String "aabbcc" is also not balanced (it contains three different letters).

*substring* of string S is a string that consists of consecutive letters in S. For example: "ompu" is a substring of "c** ompu**ter" but "cmptr" is not.

`solution` that, given a string S, returns the length of the longest balanced substring of S.

**Examples:**

1. Given S = "cabbacc", the function should return 4 ("abba" is the longest balanced substring).

3. Given S = "aaaaaaa", the function should return 0 (S does not contain a balanced substring).

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

- N is an integer within the range [1..100,000];
- string S consists only of lowercase letters (
a−z).

*balanced* if it consists of exactly two different characters and both of those characters appear exactly the same number of times. For example: "aabbab" is balanced (both 'a' and 'b' occur three times) but "aabba" is not balanced ('a' occurs three times, 'b' occurs two times). String "aabbcc" is also not balanced (it contains three different letters).

*substring* of string S is a string that consists of consecutive letters in S. For example: "ompu" is a substring of "c** ompu**ter" but "cmptr" is not.

`solution` that, given a string S, returns the length of the longest balanced substring of S.

**Examples:**

1. Given S = "cabbacc", the function should return 4 ("abba" is the longest balanced substring).

3. Given S = "aaaaaaa", the function should return 0 (S does not contain a balanced substring).

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

- N is an integer within the range [1..100,000];
- string S consists only of lowercase letters (
a−z).

*balanced* if it consists of exactly two different characters and both of those characters appear exactly the same number of times. For example: "aabbab" is balanced (both 'a' and 'b' occur three times) but "aabba" is not balanced ('a' occurs three times, 'b' occurs two times). String "aabbcc" is also not balanced (it contains three different letters).

*substring* of string S is a string that consists of consecutive letters in S. For example: "ompu" is a substring of "c** ompu**ter" but "cmptr" is not.

`solution` that, given a string S, returns the length of the longest balanced substring of S.

**Examples:**

1. Given S = "cabbacc", the function should return 4 ("abba" is the longest balanced substring).

3. Given S = "aaaaaaa", the function should return 0 (S does not contain a balanced substring).

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

- N is an integer within the range [1..100,000];
- string S consists only of lowercase letters (
a−z).

*balanced* if it consists of exactly two different characters and both of those characters appear exactly the same number of times. For example: "aabbab" is balanced (both 'a' and 'b' occur three times) but "aabba" is not balanced ('a' occurs three times, 'b' occurs two times). String "aabbcc" is also not balanced (it contains three different letters).

*substring* of string S is a string that consists of consecutive letters in S. For example: "ompu" is a substring of "c** ompu**ter" but "cmptr" is not.

`solution` that, given a string S, returns the length of the longest balanced substring of S.

**Examples:**

1. Given S = "cabbacc", the function should return 4 ("abba" is the longest balanced substring).

3. Given S = "aaaaaaa", the function should return 0 (S does not contain a balanced substring).

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

- N is an integer within the range [1..100,000];
- string S consists only of lowercase letters (
a−z).

*balanced* if it consists of exactly two different characters and both of those characters appear exactly the same number of times. For example: "aabbab" is balanced (both 'a' and 'b' occur three times) but "aabba" is not balanced ('a' occurs three times, 'b' occurs two times). String "aabbcc" is also not balanced (it contains three different letters).

*substring* of string S is a string that consists of consecutive letters in S. For example: "ompu" is a substring of "c** ompu**ter" but "cmptr" is not.

`solution` that, given a string S, returns the length of the longest balanced substring of S.

**Examples:**

1. Given S = "cabbacc", the function should return 4 ("abba" is the longest balanced substring).

3. Given S = "aaaaaaa", the function should return 0 (S does not contain a balanced substring).

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

- N is an integer within the range [1..100,000];
- string S consists only of lowercase letters (
a−z).

*balanced* if it consists of exactly two different characters and both of those characters appear exactly the same number of times. For example: "aabbab" is balanced (both 'a' and 'b' occur three times) but "aabba" is not balanced ('a' occurs three times, 'b' occurs two times). String "aabbcc" is also not balanced (it contains three different letters).

*substring* of string S is a string that consists of consecutive letters in S. For example: "ompu" is a substring of "c** ompu**ter" but "cmptr" is not.

`solution` that, given a string S, returns the length of the longest balanced substring of S.

**Examples:**

1. Given S = "cabbacc", the function should return 4 ("abba" is the longest balanced substring).

3. Given S = "aaaaaaa", the function should return 0 (S does not contain a balanced substring).

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

- N is an integer within the range [1..100,000];
- string S consists only of lowercase letters (
a−z).

*balanced* if it consists of exactly two different characters and both of those characters appear exactly the same number of times. For example: "aabbab" is balanced (both 'a' and 'b' occur three times) but "aabba" is not balanced ('a' occurs three times, 'b' occurs two times). String "aabbcc" is also not balanced (it contains three different letters).

*substring* of string S is a string that consists of consecutive letters in S. For example: "ompu" is a substring of "c** ompu**ter" but "cmptr" is not.

`solution` that, given a string S, returns the length of the longest balanced substring of S.

**Examples:**

1. Given S = "cabbacc", the function should return 4 ("abba" is the longest balanced substring).

3. Given S = "aaaaaaa", the function should return 0 (S does not contain a balanced substring).

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

- N is an integer within the range [1..100,000];
- string S consists only of lowercase letters (
a−z).

*balanced* if it consists of exactly two different characters and both of those characters appear exactly the same number of times. For example: "aabbab" is balanced (both 'a' and 'b' occur three times) but "aabba" is not balanced ('a' occurs three times, 'b' occurs two times). String "aabbcc" is also not balanced (it contains three different letters).

*substring* of string S is a string that consists of consecutive letters in S. For example: "ompu" is a substring of "c** ompu**ter" but "cmptr" is not.

`solution` that, given a string S, returns the length of the longest balanced substring of S.

**Examples:**

1. Given S = "cabbacc", the function should return 4 ("abba" is the longest balanced substring).

3. Given S = "aaaaaaa", the function should return 0 (S does not contain a balanced substring).

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

- N is an integer within the range [1..100,000];
- string S consists only of lowercase letters (
a−z).

*balanced* if it consists of exactly two different characters and both of those characters appear exactly the same number of times. For example: "aabbab" is balanced (both 'a' and 'b' occur three times) but "aabba" is not balanced ('a' occurs three times, 'b' occurs two times). String "aabbcc" is also not balanced (it contains three different letters).

*substring* of string S is a string that consists of consecutive letters in S. For example: "ompu" is a substring of "c** ompu**ter" but "cmptr" is not.

`solution` that, given a string S, returns the length of the longest balanced substring of S.

**Examples:**

1. Given S = "cabbacc", the function should return 4 ("abba" is the longest balanced substring).

3. Given S = "aaaaaaa", the function should return 0 (S does not contain a balanced substring).

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

- N is an integer within the range [1..100,000];
- string S consists only of lowercase letters (
a−z).

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