BinarySearch 0459 Arithmetic Sequences

Problem statement

https://binarysearch.com/problems/Arithmetic-Sequences/

Solution

Equal to Leetcode 0413. Arithmetic Slices.

Complexity

It is O(n) for time and space.

Code

class Solution:
    def solve(self, A):
        B =  [j-i for i,j in zip(A, A[1:])]
        return sum(((2*len(list(j))-1)**2-1)//8 for i, j in groupby(B))