413. Arithmetic Slices

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