18. Arithmetic Slices

class Solution {
    public int numberOfArithmeticSlices(int[] A) {
        int[] dp = new int[A.length]; 
        int res = 0; 
        for(int i = 2; i < dp.length; i++) {
            
            if(A[i]-A[i-1] == A[i-1]-A[i-2]) {
                dp[i]=1+dp[i-1];
                res+=dp[i];
            }
        }
        return res;
    }
}

public class Solution {
    public int numberOfArithmeticSlices(int[] A) {
        int dp = 0;
        int sum = 0;
        for (int i = 2; i < A.length; i++) {
            if (A[i] - A[i - 1] == A[i - 1] - A[i - 2]) {
                dp = 1 + dp;
                sum += dp;
            } else
                dp = 0;
        }
        return sum;
    }
}	

public class Solution {
    public int numberOfArithmeticSlices(int[] A) {
        int count = 0;
        int sum = 0;
        for (int i = 2; i < A.length; i++) {
            if (A[i] - A[i - 1] == A[i - 1] - A[i - 2]) {
                count++;
            } else {
                sum += (count + 1) * (count) / 2;
                count = 0;
            }
        }
        return sum += count * (count + 1) / 2;
    }
}