RatingConsectiveDecresing

https://leetcode.com/discuss/interview-question/1554594/ama‍‍‌‌‌‌‍‍‌‍‌‍‌‍‌‍‌‌‌‍z

There is a new product launched and its customer ratings are being recorded in an array. The ratings are being monitored and analyzed if there is any decrease in the ratings. Find the number of periods in which the rating is consecutively decreasing.

Example - Ratings = [4,3,5,4,3] Periods (in other words sub arrays in which ratings are decreasing): One day periods = [4],[3],[5],[4],[3] (count of subarrays is 5) Two day periods = [4,3],[5,4],[4,3] (count of subarrays is 3) 3 day periods = [5,4,3] (count of subarrays is 1) So, the output for this example will be 9 (5 + 3 + 1)

找到连续下降的长度，他们能成的是(n-1)*n/2; 最后再加上 以1为长度的

public static int periodsOfDecreaseRating(int[] ratings)
    {
        int decreasing = 1;
        int count = 0;
        for(int i = 1; i< ratings.length; i++)
        {
            if(ratings[i]  < ratings[i-1])
            {
                decreasing++;
            }
            else
            {
                count += decreasing*(decreasing-1)/2;
                decreasing = 1;
            }
        }
        // 这种情况就是数组一直在下降
        if(decreasing > 1)
        {
            count += decreasing*(decreasing-1)/2;
        }
        return count + ratings.length;
    }