# 413. Arithmetic Slices

#### Medium

***

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`

```python
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
```