counting pairs.java

import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.function.*;
import java.util.regex.*;
import java.util.stream.*;
import static java.util.stream.Collectors.joining;
import static java.util.stream.Collectors.toList;



class Result {

    /*
     * Complete the 'countPairs' function below.
     *
     * The function is expected to return an INTEGER.
     * The function accepts following parameters:
     *  1. INTEGER_ARRAY numbers
     *  2. INTEGER k
     */

    public static int countPairs(List<Integer> numbers, int k) {
    // Write your code here
     HashSet<Integer> hLow = new HashSet<>();

        HashSet<Integer> hHigh = new HashSet<>();

       // List<Pair> ret = new ArrayList<>();

       int count = 0;

        for (int i : numbers) {

            hLow.add(i);

            hHigh.add(i+k);

        }

        for (int i : hHigh) {

            if (hLow.contains(i)) {

                // ret.add(new Pair(i-k, i));

                count++;

            }

        }

        return count;

   

    }

}

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

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

        List<Integer> numbers = IntStream.range(0, numbersCount).mapToObj(i -> {
            try {
                return bufferedReader.readLine().replaceAll("\\s+$", "");
            } catch (IOException ex) {
                throw new RuntimeException(ex);
            }
        })
            .map(String::trim)
            .map(Integer::parseInt)
            .collect(toList());

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

        int result = Result.countPairs(numbers, k);

        bufferedWriter.write(String.valueOf(result));
        bufferedWriter.newLine();

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