E0059.cpp

/*
Problem Statement: https://www.hackerrank.com/challenges/beautiful-triplets/problem
*/

#include <iostream>
#include <vector>
#include <unordered_set>

using namespace std;

int beautifulTriplets(int d, vector<int> arr) {
	int count = 0;
	unordered_set<int> hashSet;
	for(int i=0 ; i<arr.size() ; i++){
		bool isBeautifulTriplet = (hashSet.find(arr[i]-d) != hashSet.end()) && (hashSet.find(arr[i]-2*d) != hashSet.end());
		if(isBeautifulTriplet)
			count++;
		hashSet.insert(arr[i]);
	}
	return count;
}

int main()
{
	int n, d, num;
	vector<int> arr;
	cin>>n>>d;
	for(int i=0 ; i<n ; i++){
		cin>>num;
		arr.push_back(num);
	}
	cout<<beautifulTriplets(d, arr);
	return 0;
}