arithmetic slices leetcode

class Solution {
public:
    // Time Complexity:- O(N)
    // Space Complexity:- O(N)
    int numberOfArithmeticSlices(vector<int>& nums) {
        int n = nums.size();

        // dp[i] = number of arithmetic subarrays ending at index i
        vector<int> dp(n+1);

        for(int i=2;i<n;i++){
            // if the three element difference is same, extend the subarray
            if(nums[i]-nums[i-1]==nums[i-1]-nums[i-2]){
                dp[i] = 1 + dp[i-1];
            }
        }

        return accumulate(dp.begin(),dp.end(),0);
    }
};