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# Program to find number of arithmetic sequences from a list of numbers in Python?

Suppose we have a list of numbers called nums, we have to find the number of contiguous arithmetic sequences of length ≥ 3. As we know an arithmetic sequence is a list of numbers where the difference between one number and the next number is the same.

So, if the input is like nums = [6, 8, 10, 12, 13, 14], then the output will be 4, as we have the arithmetic sequences like: [6, 8, 10] [8, 10, 12] [6, 8, 10, 12] [12, 13, 14]

To solve this, we will follow these steps −

count := 0, ans := 0

for i in range 2 to size of nums, do

if nums[i] - nums[i - 1] is same as nums[i - 1] - nums[i - 2], then

count := count + 1

otherwise,

ans := ans + quotient of (count * (count + 1)) / 2

count := 0

if count is non-zero, then

ans := ans + quotient of (count *(count + 1)) / 2

return ans

Let us see the following implementation to get better understanding:

## Example

class Solution: def solve(self, nums): count = 0 ans = 0 for i in range(2, len(nums)): if nums[i] - nums[i - 1] == nums[i - 1] - nums[i - 2]: count += 1 else: ans += (count * (count + 1)) // 2 count = 0 if count: ans += (count * (count + 1)) // 2 return ans ob = Solution() nums = [6, 8, 10, 12, 13, 14] print(ob.solve(nums))

## Input

[6, 8, 10, 12, 13, 14]

## Output

4

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