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Given a string, remove characters until the string is made up of any two alternating characters. When you choose a character to remove, all instances of that character must be removed. Determine the longest string possible that contains just two alternating letters.

Example

Delete a, to leave bcdbd. Now, remove the character c to leave the valid string bdbd with a length of 4. Removing either b or d at any point would not result in a valid string. Return .

Given a string , convert it to the longest possible string made up only of alternating characters. Return the length of string . If no string can be formed, return .

Function Description

Complete the alternate function in the editor below.

alternate has the following parameter(s):

  • string s: a string

Returns.

  • int: the length of the longest valid string, or if there are none

Input Format

The first line contains a single integer that denotes the length of .
The second line contains string .

Constraints

Sample Input

STDIN       Function
-----       --------
10          length of s = 10
beabeefeab  s = 'beabeefeab'

Sample Output

5

Explanation

The characters present in are a, b, e, and f. This means that must consist of two of those characters and we must delete two others. Our choices for characters to leave are [a,b], [a,e], [a, f], [b, e], [b, f] and [e, f].

If we delete e and f, the resulting string is babab. This is a valid as there are only two distinct characters (a and b), and they are alternating within the string.

If we delete a and f, the resulting string is bebeeeb. This is not a valid string because there are consecutive e‘s present. Removing them would leave consecutive b's, so this fails to produce a valid string .

Other cases are solved similarly.

babab is the longest string we can create.

Limbajul de programare folosit: python3

Cod:

#!/bin/python3

def alternate(s):
    chars = sorted(set(s))
    best = 0
    for i in range(len(chars)):
        for j in range(i + 1, len(chars)):
            a, b = chars[i], chars[j]
            t = [ch for ch in s if ch == a or ch == b]
            if len(t) < 2:
                continue
            ok = True
            for k in range(1, len(t)):
                if t[k] == t[k - 1]:
                    ok = False
                    break
            if ok:
                best = max(best, len(t))
    return best

if __name__ == '__main__':
    _ = int(input().strip())
    s = input().strip()
    print(alternate(s))

Scor obtinut: 1.0

Submission ID: 464589777

Link challenge: https://www.hackerrank.com/challenges/two-characters/problem

Two Characters