SKP's Java Problem Solving Series : Usernames Changes (HackerRank)

[Question/Problem Statement is Adapted from HackerRank]

Algorithms/Data Structures - [Problem Solving] 

There is a Specific Need for Changes in a List of Usernames. In a given List of Usernames - For Each Username - If the Username can be Modified and Moved Ahead in a Dictionary. The Allowed Modification is that Alphabets can change Positions in the Given Username.

Example

usernames[] = {"Aab", "Cat"}

 

"Aab" cannot be changed to another unique string matching the above rule - Hence, It can Never Find a Place Ahead in the Dictionary. Hence, Output will be "NO". "Cat" can be Changed to "Act", "Atc", "Tca", "Tac", "Cta" and Definitely "Act" will Find a Place Before "Cat" in the Dictionary. Hence, Output will be "YES".

[Function Description]
Complete the function possibleChanges in the Editor Below.
 

possibleChanges has the Following Parameters:
String usernames[n]: An Array of User Names
 

Returns String[n]: An Array with "YES" or "NO" Based on Feasibility
(Actual Question Says String Array, But Signature is List of Strings)

Constraints
• [No Special Constraints Exist, But Cannot Recall Exactly]

Input Format
"The First Line Contains an Integer, n, the Number of Elements in Usernames.", 

"Each Line of the n Subsequent Lines (where 0 < i < n) contains a String usernames[i]."        

[Sample Case 0 - Sample Input For Custom Testing]        
8      
Aab 

Cat

Pqrs

Buba

Bapg

Sungi

Lapg

Acba

       

Sample Output (Each Should Be on a Separate Line)

NO YES NO YES YES YES YES YES

  

______________ 

 

 
[Explanation of the Solution]
This is again a Good Question from Hacker Rank to Test Your Logic / Problem Solving Abilities. The Core Point to Handle is that For Each Combination of 2 Alphabets that Exists in the Username String > We Need to Check if the Latter Occuring Character (ASCII) is Less than the Former Occuring Character (ASCII). For Example in the String "Bapg" - For a Selection of "Ba" from "Bapg" - We have "a" Occuring Before "B" in the English Alphabet. We can Have Two Loops (One Nested) to Decide for a Combination of Each Two Alphabets. The Time Complexity of this Solution is O(n^2).

 

________________  

 

[Source Code, Sumith Puri (c) 2021 - Free to Use & Distribute]

import static java.util.stream.Collectors.joining;
import static java.util.stream.Collectors.toList;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.IntStream;

/*
 * HackerRank Problem Solving - Speak Ur Mind, But Ride a Fast Horse.
 * ~ Sumith Kumar Puri (c) 2021 ~ -- ~ Bengaluru, Karnataka, India ~
 * 
 */
class UsernamesChangesLogic {

	public static List<String> possibleChanges(List<String> usernames) {

		List<String> solutionStr = new ArrayList<String>();
		boolean bobbysFlag = false;
		for (String username : usernames) {

			bobbysFlag = false;
			String currName = username.toLowerCase();
			for (int i = 0; i < currName.length(); i++) {

				int a = currName.charAt(i);
				for (int j = i + 1; j < currName.length(); j++) {

					int b = currName.charAt(j);
					if (b < a) {
						bobbysFlag = true;
						break;
					}
				}
				if (bobbysFlag) {
					solutionStr.add("YES");
					break;
				}
			}
			if (!bobbysFlag)
				solutionStr.add("NO");
		}

		return solutionStr;
	}
}

public class UsernamesChanges {

	public static final String OUTPUT_PATH = "PROVIDE_ABSOLUTE_INPUT_FILE_NAME";

	public static void main(String[] args) throws IOException {
		BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
		BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(OUTPUT_PATH));

		int usernamesCount = Integer.parseInt(bufferedReader.readLine().trim());

		List<String> usernames = IntStream.range(0, usernamesCount).mapToObj(i -> {
			try {
				return bufferedReader.readLine();
			} catch (IOException ex) {
				throw new RuntimeException(ex);
			}
		}).collect(toList());

		List<String> result = UsernamesChangesLogic.possibleChanges(usernames);

		bufferedWriter.write(result.stream().collect(joining("\n")) + "\n");

		bufferedReader.close();
		bufferedWriter.close();
	}
}

Happy Problem Solving using Java!