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413. Arithmetic Slices
Description
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
Solutions
-
class Solution { public int numberOfArithmeticSlices(int[] nums) { int ans = 0, cnt = 0; int d = 3000; for (int i = 0; i < nums.length - 1; ++i) { if (nums[i + 1] - nums[i] == d) { ++cnt; } else { d = nums[i + 1] - nums[i]; cnt = 0; } ans += cnt; } return ans; } } -
class Solution { public: int numberOfArithmeticSlices(vector<int>& nums) { int ans = 0, cnt = 0; int d = 3000; for (int i = 0; i < nums.size() - 1; ++i) { if (nums[i + 1] - nums[i] == d) { ++cnt; } else { d = nums[i + 1] - nums[i]; cnt = 0; } ans += cnt; } return ans; } }; -
class Solution: def numberOfArithmeticSlices(self, nums: List[int]) -> int: ans = cnt = 0 d = 3000 for a, b in pairwise(nums): if b - a == d: cnt += 1 else: d = b - a cnt = 0 ans += cnt return ans -
func numberOfArithmeticSlices(nums []int) (ans int) { cnt, d := 0, 3000 for i, b := range nums[1:] { a := nums[i] if b-a == d { cnt++ } else { d = b - a cnt = 0 } ans += cnt } return } -
function numberOfArithmeticSlices(nums: number[]): number { let ans = 0; let cnt = 0; let d = 3000; for (let i = 0; i < nums.length - 1; ++i) { const a = nums[i]; const b = nums[i + 1]; if (b - a == d) { ++cnt; } else { d = b - a; cnt = 0; } ans += cnt; } return ans; }