Diff pairs

/* package codechef; // don't place package name! */
import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
public class Main
{
    public static void main (String[] args) throws java.lang.Exception,IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        String[] firstLine = br.readLine().split(" ");
        int N = Integer.parseInt(firstLine[0]);
        int K = Integer.parseInt(firstLine[1]);

        String[] numsStr = br.readLine().split(" ");
        int[] nums = new int[N];
        for (int i = 0; i < N; i++) {
            nums[i] = Integer.parseInt(numsStr[i]);
        }
        Arrays.sort(nums);
        getC(N, K, nums);
    }

    private static void getC(int N, int K, int[] nums) {
        int i = 0, j = 1;
        long c = 0;
        while (j < N) {
            int d = nums[j] - nums[i];
            if (d < K) {
                j++;
            } else if (d > K) {
                i++;
                if (i == j) {
                    j++;
                }
            } else {
                int c1 = 0, c2 = 0, p = nums[i], q = nums[j];
                if (d == 0) {
                    while (nums[i] == p) {
                        c1++;
                        i++;
                        j++;
                    }
                    c += c1 * (c1 - 1) / 2;
                    // System.out.println("P1 " + c);
                    // return;
                } else {
                    while (i < N &&nums[i] == p) {
                        c1++;
                        i++;
                    }
                    while (j < N && nums[j] == q) {
                        c2++;
                        j++;
                    }
                    c += c1 * c2;

                }
            }
        }
        System.out.println(c);
    }
}