(Hacker Rank) Pairs - Solution

Link to the problem: https://www.hackerrank.com/challenges/pairs

The solution below sorts the given array. Then, for every element in the array, we apply the following steps:

• Sum the element and the value of K;
• Call the Binary Search method to find out if the array contains the result of the sum;
• If the array contains the result of the sum, then we found a pair.

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {
    static int[] elements;
   
    static boolean binSearch(int lo, int hi, int value) {
        if (lo > hi) {
            return false;
        }   
       
        int m = (lo+hi)/2;
        if (elements[m] < value) {
            return binSearch(m+1, hi, value);
        }
        if (elements[m] > value) {
            return binSearch(lo, m-1, value);
        }
        else {
            return true;
        }
    }
   
    static int pairs(int k) {
        int count = 0;
        for (int i = 0; i < elements.length; i++) {
            int diff = elements[i]+k;
            if (binSearch(i+1, elements.length-1, diff)) {
                count++;
            }
        }
        return count;
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
       
        String line = sc.nextLine();
        String[] s = line.split(" ");
       
        int numElements = Integer.parseInt(s[0]);
        int value = Integer.parseInt(s[1]);
       
        elements = new int[numElements];
        line = sc.nextLine();
        s = line.split(" ");
        for(int i = 0; i < numElements; i++) {
            elements[i] = Integer.parseInt(s[i]);
        }
       
        Arrays.sort(elements);
        System.out.println(pairs(value));
    }
}