Given a sequence of integers , a triplet is beautiful if:
Given an increasing sequence 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 .
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
The first line contains space-separated integers and , the length of the sequence and the beautiful difference.
The second line contains space-separated integers .
Print a single line denoting the number of beautiful triplets in the sequence.
7 3 1 2 4 5 7 8 10
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 in Python
def beautifulTriplets(d, arr): a = set(arr) return len([1 for i in arr if i+d in a and i+d*2 in a]) n,d = map(int,input().split()) arr = list(map(int,input().split())) print(beautifulTriplets(d, arr))