BeautifulTripletsHR.py

"""
Given a sequence of integers , a triplet  is beautiful if:

Given an increasing sequenc of integers and the value of , count the number of beautiful triplets in the sequence.

For example, the sequence  and . There are three beautiful triplets, by index: . To test the first triplet,  and .

Function Description

Complete the beautifulTriplets function in the editor below. It must return an integer that represents the number of beautiful triplets in the sequence.

beautifulTriplets has the following parameters:

d: an integer
arr: an array of integers, sorted ascending
Input Format

The first line contains  space-separated integers  and , the length of the sequence and the beautiful difference.
The second line contains  space-separated integers .

Constraints

Output Format

Print a single line denoting the number of beautiful triplets in the sequence.

Sample Input

7 3
1 2 4 5 7 8 10
Sample Output

3
Explanation

The input sequence is , and our beautiful difference . There are many possible triplets , but our only beautiful triplets are  ,  and  by value not index. Please see the equations below:





Recall that a beautiful triplet satisfies the following equivalence relation:  where .


"""
# SOLUTION
def find_last(l,index , d) :
    current_ele = l[index]
    return [element for element in l[index + 1:] if element - current_ele == d]

def find_first(l,index , d) :
    current_ele = l[index]
    return [element for element in l[:index] if current_ele - element == d]

def beautifulTriplets(d , l) :
    l_size = len(l)
    count = 0
    while l_size >= 2 :
        l_size -= 1
        count += len(find_first(l,l_size , d))*len(find_last(l,l_size , d))
    return count

nd = input().split()
n = int(nd[0])
d = int(nd[1])
l = list(map(int, input().rstrip().split()))
result = beautifulTriplets(d, l)
print(result)