Two Characters in Algorithm | HackerRank Programming Solutions | HackerRank Problem Solving Solutions in Java [💯Correct]

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Introduction To Algorithm

The word Algorithm means “a process or set of rules to be followed in calculations or other problem-solving operations”. Therefore Algorithm refers to a set of rules/instructions that step-by-step define how a work is to be executed upon in order to get the expected results. 

Advantages of Algorithms:

  • It is easy to understand.
  • Algorithm is a step-wise representation of a solution to a given problem.
  • In Algorithm the problem is broken down into smaller pieces or steps hence, it is easier for the programmer to convert it into an actual program.

Link for the ProblemTwo Characters– Hacker Rank Solution

Two Characters – Hacker Rank Solution


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.


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


  • 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 .


image 86

Sample Input

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

Sample Output



The characters present in  are abe, 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 .

Two Characters – Hacker Rank Solution
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;
public class Solution {
    public static void main(String[] args) {
       Scanner in=new Scanner(;
        int n=in.nextInt();
        String res="";
        for(int i=0;i<26;i++){
            for(int j=i+1;j<26;j++){
                char a=(char)('a'+i);
                char b=(char)('a'+j);
                String cur="";
                for(int k=0;k<n;k++){
                    if (s.charAt(k)==a || s.charAt(k)==b) {
                if (cur.length()<res.length()) continue;
                if (isGood(cur)) res=cur;
    public static boolean isGood(String s){
        if (s.length()==1) return false;
        for(int i=1;i<s.length();i++){
            if (s.charAt(i)==s.charAt(i-1)) return false;
        return true;

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