## Description

https://leetcode.com/problems/arithmetic-slices/

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:3Explanation: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`

## Explanation

Iterate each number and to find all arithmetic slices starting from each number.

## Python Solution

```
class Solution:
def numberOfArithmeticSlices(self, nums: List[int]) -> int:
if len(nums) < 3:
return 0
results = []
for i in range(len(nums) - 1):
prev = nums[i]
diff = None
subarrays = [nums[i]]
for j in range(i + 1, len(nums)):
if diff == None:
diff = nums[j] - prev
prev = nums[j]
subarrays.append(nums[j])
else:
if nums[j] - prev == diff:
subarrays.append(nums[j])
prev = nums[j]
if len(subarrays) >= 3:
results.append(list(subarrays))
else:
break
return len(results)
```

- Time Complexity: O(N).
- Space Complexity: O(N).