413.cpp

class Solution {
public:
    int numberOfArithmeticSlices(vector<int>& A) {
        int count = 0;
        int added = 0;
        int n = A.size();
        for(int i = 2; i < n; i++) {
            if (A[i-1] - A[i] == A[i-2] - A[i-1]) {
                count += ++added;
            } else {
                added = 0;
            }
        }
        return count;
    }
};