Arithmetic Slices
Problem Statement - link #
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.
Examples #
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(vector<int>& nums) {
if(nums.size() <= 2)return 0;
int count = 0, ans = 0;
for(int i = 0; i < nums.size() - 2; i++){
if(nums[i+1] - nums[i] == nums[i+2] - nums[i+1]){
count++;
}
else{
ans += ((count * (count+1)) / 2);
count = 0;
}
}
if(count) ans += ((count * (count+1)) / 2);
return ans;
}
};