HACKRNDM.java

/** https://www.spoj.com/problems/OPCPIZZA/ #binary-search #two-pointer */
import java.io.*;
import java.util.*;
import java.util.Arrays;

class HACKRNDM {
  public static void main(String[] args) {
    MyScanner sc = new MyScanner(System.in);
    int n = sc.nextInt();
    int k = sc.nextInt();
    int[] arr = new int[n];
    int tmp;
    for (int i = 0; i < n; i++) {
      tmp = sc.nextInt();
      arr[i] = tmp;
    }
    Arrays.sort(arr);
    int count = 0;
    /* two pointer
    left = 0
    right = 1

    arr[right] - arr[left]
    < diff: increase right
    > diff: increase left
    = diff: increase left, right
    */
    int left = 0, right = 1;
    while (right < arr.length) {
      if (arr[right] - arr[left] == k) {
        count++;
        right++;
        left++;
      } else if (arr[right] - arr[left] > k) {
        left++;
      } else {
        right++;
      }
    }
    System.out.println(count);
  }
}

class MyScanner {
  BufferedReader br;
  StringTokenizer st;

  public MyScanner(InputStream is) {
    br = new BufferedReader(new InputStreamReader(is));
  }

  String next() {
    while (st == null || !st.hasMoreElements()) {
      try {
        st = new StringTokenizer(br.readLine());
      } catch (IOException e) {
        e.printStackTrace();
      }
    }
    return st.nextToken();
  }

  int nextInt() {
    return Integer.parseInt(next());
  }

  long nextLong() {
    return Long.parseLong(next());
  }

  double nextDouble() {
    return Double.parseDouble(next());
  }

  String nextLine() {
    String str = "";
    try {
      str = br.readLine();
    } catch (IOException e) {
      e.printStackTrace();
    }
    return str;
  }
}