Problem
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
Solution (Java)
class Solution {
public int numberOfArithmeticSlices(int[] nums) {
int sum = 0;
int curr = 0;
for (int i = 2; i < nums.length; i++) {
if (nums[i] - nums[i - 1] == nums[i - 1] - nums[i - 2]) {
curr++;
sum += curr;
} else {
curr = 0;
}
}
return sum;
}
}
Explain:
nope.
Complexity:
- Time complexity : O(n).
- Space complexity : O(n).