[알고리즘] 51. Beautiful Triplets

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 .

답 : 

#!/bin/python3

import math

import os

import random

import re

import sys

# Complete the beautifulTriplets function below.

if __name__ == '__main__':

n,d=map(int,input().split())

arr=list(map(int,input().split()))

cnt = 0

for i in range(len(arr)):

if arr[i]+d in arr and arr[i]+2*d in arr:

cnt += 1

print(cnt)

A, A+d, A+2d 가 있는지를 묻는 문제!

A+d와 A+2d가 있는지를 확인하고 있으면 count += 1 해줬다.