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: 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
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).