2025-12-15 21:33:29 +0300 MSK

class Solution:
    def getDescentPeriods(self, prices: List[int]) -> int:
        n = len(prices)
        res = 1  # total number of smooth descending periods, initial value is dp[0]
        prev = 1  # total number of smooth descending periods ending with the previous element, initial value is dp[0]
        # traverse the array starting from 1, and update prev and the total res according to the recurrence relation
        for i in range(1, n):
            if prices[i] == prices[i - 1] - 1:
                prev += 1
            else:
                prev = 1
            res += prev
        return res