Two Characters Hackerrank Problem’s Solution

Two Characters Hackerrank

There are two characters, take it as x & y.We have different strings which can be made through these characters in an alternate way like xyxyxy or yxyxyx but not xxyy or xyyx or so on


Now, there is a twist that you can convert some string ‘s’ to string ‘t’ by deleting characters from ‘s’. When you delete a character from s, you must delete all occurrences of it in s. For example, if s = abaacdabd and you delete the character a, then the string becomes bcdbd.

Suppose you have provided a string S, convert it to the possible longest String T using the same alphabet then print the length of the newly string T in a new Line otherwise if the string T is not possible to form then print its length to 0.


The problem is of hackerrank to go to that use the below link:

  • Input Format

The first line contains a single integer denoting the length of s.

The second line contains string s.


  • Constraints
    Here, an only contains lowercase English alphabetic letters (i.e., a to z).


  • Output text

Print a single integer denoting the maximum length of t for the given s; if it is not possible to form string t, print 0 instead.


Sample Input

Sample Output




  • The characters present in s are a, b, e, and f. This means that must consist of two of those characters.
  • If we delete e and f, the resulting string is babab. This is a valid t 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 t because there is three consecutive e’s present.
  • If we delete the only e, the resulting string is babfab. This is not a valid string t because it contains three distinct characters.

Thus, we print the length of babab, which is 5, as our answer.


Case: s only consists of 1 distinct character.Because string t must contain exactly two distinct characters that alternate throughout the string, we cannot form t in this case so the answer will be 0.
Case: s consists of two or more distinct characters.
Choose two characters to be present in string t and delete all other characters from s.
Check the resulting string to see if it’s a valid t. In other words, determine if the two characters alternate or not. If yes, then the string is valid and you simply need to simply save its length; otherwise, it’s invalid and we consider its length to be 0.
Check all possible pairs of characters and then print the maximum of these lengths.



from itertools import combinations
#include <bits/stdc++.h>
using namespace std;

int make_string(string str, char a, char b)
    int len = str.size();
    string temp = "";
    char last;

    for(int i=0; i<len; i++)
        if(str[i]== a || str[i] == b)

    len = temp.size();
    if(len <= 1)
        return 0;

    last = temp[0];
    for(int i=1; i<len; i++)
        if(temp[i] == last)
            return 0;
        last = temp[i];
    return len;

int main(){
string s; char a, b;

cout<<make_string(s, a, b);
return 0;


def meet_pattern(s):
return all(s[i-1] != s[i] for i in range(1,len(s)))

s_len = int(input().strip())
s = input().strip()
letters = set(s)
max_len = 0
for pair in combinations(letters,2):
substr = "".join(i for i in s if i in pair)
if meet_pattern(substr):
max_len = max(max_len, len(substr))



import sys
assert s.isalpha()
for i in range(0,26):
    for j in range(0,26):
        if i==j:
        p1 = i
        p2 = j
        flag = 1
        l = 0
        for c in s:
            if ord(c)-ord('a')!=p1 and ord(c)-ord('a')!=p2:
            if ord(c)-ord('a') == p1:
                l = l + 1
                p1,p2 = p2,p1
                flag = 0
        if flag == 1 and l>1:

print ans

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