Java Hashset HackerRank Solution | Programming Blog

Java Hashset HackerRank Solution with Explanation

 

Problem Statement :-

In computer science, a set is an abstract data type that can store certain values, without any particular order, and no repeated values. {1,2,3} is an example of a set, but {1,2,2} is not a set. Today you will learn how to use sets in java by solving this problem.

You are given n pairs of strings. Two pairs (a,b) and (c,d) are identical if a = c and b = d. That also implies (a,b) is not same as (b,a). After taking each pair as input, you need to print number of unique pairs you currently have.

See full problem description in HackerRank Website :-

https://www.hackerrank.com/challenges/java-hashset/problem

Let's see solution of problem.

import java.util.HashSet;
import java.util.Scanner;

public class Solution {

    public static void main(String[] args) {
        Scanner s = new Scanner(System.in);
        System.out.println("Enter total pair");
        int t = s.nextInt();
        String [] pair_left = new String[t];
        String [] pair_right = new String[t];
        
        System.out.println("Enter string pair");
        for (int i = 0; i < t; i++) {
            pair_left[i] = s.next();
            pair_right[i] = s.next();
        }
        
        HashSet<String> set = new HashSet<>();
        
        for (int i = 0; i < t; i++) {
            set.add(pair_left[i] + " , " + pair_right[i]);
            System.out.println(set.size());
        }

    }

}

Input :-

    5
    john tom
    john mary
    john tom
    mary anna
    mary anna 

Output :-

    1
    2
    2
    3
    3

Explanation :-

1. Declare new HashSet.
2. Loop through given total number of pairs.
3. Add pair into set, separated by comma. (We can take any separator).
4. Check size of set. If Given pair is matched in set then set does not store that pair into it and HashSet size remains same.

We must add some separator in to above solution, because if there is given pair like "abc def" and after there is another pair like "ab cdef" then without separator it HashSet count same value "abcdef" and we got wrong output.

If we include any separator then, 

pair 1 : "abc def" = abc,def
pair 2 : "ab cdef" = ab,cdef

Both pair count differently and we got correct output.

If you have any query regarding above solution comment down. I am happy to resolve it.

Happy Coding.

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