Arithmetic Slices

MediumDynamic Programming1d dp

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Problem

An array is **arithmetic** when it has at least three elements and every pair of neighbouring elements differs by the same amount. [1,3,5,7], [7,7,7] and [3,-1,-5] are arithmetic; [1,1,2] is not. Given an integer array nums, return how many contiguous subarrays of nums are arithmetic. Subarrays at different positions count separately, even if they hold the same values.

Examples

Input: nums = [1,2,3,4]
Output: 3
The arithmetic subarrays are [1,2,3], [2,3,4] and [1,2,3,4].
Input: nums = [1]
Output: 0
A single element is too short.

Constraints

  • 1 <= nums.length <= 5000
  • -1000 <= nums[i] <= 1000

What the interviewer grades

A correct solution is one of five scores. The report also grades problem understanding (did you clarify inputs and edge cases before coding), problem solving, communication while you work, code quality, and testing. See a sample report, or read up on the pattern in the lessons.

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