2 Solutions : Using JavaScript And Java

SolutionOne.js

//	Save File As 'UniquePairs.js'
//	To Run : node UniquePairs Or node UniquePairs.js

//  Count Pairs
function sortAndCount(n, arr) {

	// Sort Array
    let sorted = arr.sort( (a,b) => a - b);
    let pairs = 0;

    for (let i = 0; i < n - 1; i = i + 2) {
        if ( sorted[i] === sorted[i + 1]) {
            pairs++;
        }
    }
    
    return pairs;
}

//  Input
n = 17
arr = [10, 10, 10, 10, 20, 30, 30, 30, 30, 30, 30, 30, 40, 40, 40, 40, 40];

//  Output Total Pairs
console.log(sortAndCount(n, arr))

SolutionTwo.java

//	Save File As 'UniquePairs.java'
//	To Compile And Run : javac UniquePairs.java && java UniquePairs

import java.util.*;

public class UniquePairs {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int N = scanner.nextInt();
        HashMap<Integer, Integer> counter = new HashMap<>();
		//	Input
        for (int i = 0; i < N; i++) {
            int sock = scanner.nextInt();
            if (counter.containsKey(sock)) {
                counter.put(sock, counter.get(sock) + 1);
            } else {
                counter.put(sock, 1);
            }
        }
		
        int totalPairs = 0;
		
		//	Sum Total Pairs
        for (int key : counter.keySet()) {
            totalPairs += Math.floor(counter.get(key) / 2);
        }
		
		// Output Total Pairs
        System.out.println(totalPairs);
        scanner.close();
    }
}

PROBLEM :

Rohit works at a clothing store.

He has a large pile of socks that he must pair by colour for sale.

Given an array of integers representing the color of each sock.

Determine how many pairs of socks with matching colors there are.

For example:-

There are n = 17 with color

arr = [1,1,1,1,2,3,3,3,3,3,3,3,4,4,4,4,4]

There is two pair of color 1 ,three of color 3 and two of color 4 . 

There are three odd socks left, one of color 2 , color 3 and color 4 . 

The number of pair is 7 .

SOLUTION :

• JavaScript

• Java