413. Arithmetic Slices

Medium

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An integer array is called arithmetic if it consists of at least three elements and if the difference between any two consecutive elements is the same.

• For example, [1,3,5,7,9], [7,7,7,7], and [3,-1,-5,-9] are arithmetic sequences.

Given an integer array nums, return the number of arithmetic subarrays of nums.

A subarray is a contiguous subsequence of the array.

Example 1:

Input: nums = [1,2,3,4]
Output: 3
Explanation: We have 3 arithmetic slices in nums: [1, 2, 3], [2, 3, 4] and [1,2,3,4] itself.

Example 2:

Input: nums = [1]
Output: 0

Constraints:

• 1 <= nums.length <= 5000

• -1000 <= nums[i] <= 1000

class Solution:
    def numberOfArithmeticSlices(self, nums: List[int]) -> int:
        total = 0 # Total subarrays
        count = 0 # Number of subarrays we get by adding current index element
        for index in range(2, len(nums)):
            if nums[index-1] - nums[index-2] == nums[index] - nums[index-1]:
                count += 1
                total += count
            else:
                count = 0
        return total