BeautifulTriplets.java

//O(nlogn) currently, using binary search, as sorted order is given

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

public class Solution {

    public int search(int[] arr,int left,int right,int value) 
    {
    int found=0,copy;
    while(left<=right)
    {
        int mid = (left+right)/2;
    if(value==arr[mid])
        {
        found=1;
        copy = mid;
        return mid;
    }
    else
        {
        if(value<arr[mid])
            right=mid-1;
        else
            left=mid+1;
    }
}
    if(found==0)
        {
        return -1;
    }

    return -1;


}

public static void main(String[] args) {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */

    int n,d;
    Scanner reader = new Scanner(System.in);

    n= reader.nextInt();
    d=reader.nextInt();
    int[] arr = new int[n];

    for(int i=0;i<n;i++)
        {
        arr[i]=reader.nextInt();
    }

    int count=0,value1,value2,index1,index2;

    for(int i=0;i<n;i++)
        {
        value1 = arr[i]+d;
        index1 = search(arr,i+1,n-1,value1);
        if(index1!=-1 && index1!=n-1)
            {
            value2 = arr[index1]+d;
            index2= search(arr,index1+1,n-1,value2);
            if(index2!=-1)
                count++;

        }
    }

    System.out.println(count);
}
}