r5NJIL - Online Java Compiler & Debugging Tool

import java.util.Arrays;
import java.util.Scanner;
class PairsLessThanK {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        // Read input values
        long n = sc.nextLong();
        long k = sc.nextLong();
        long[] b = new long[(int)n];
        for (int i = 0; i < n; i++) {
            b[i] = sc.nextLong();
        }
        long count = 0;

        // Sort the array
        Arrays.sort(b);

        // Two-pointer approach
        for (int i = 0, j = (int)n - 1; i < n; i++) {
            long d = b[i] + b[j];
            while(d>k && i!=j){
                j--;
                d = b[i] + b[j];
            }
            // if we have reached a point where i,j same then we would just be recounting.. so break
            // i we want <j
            if(i==j){
                break;
            }
            System.out.println(i + " " + j);
            count += (j - i);
        }
        System.out.println(count);
    }
}