2110.GetDescentPeriods.cs

// 2110. Number of Smooth Descent Periods of a Stock
// You are given an integer array prices representing the daily price history of a stock, 
// where prices[i] is the stock price on the ith day.

// A smooth descent period of a stock consists of one or more contiguous days such that the price on each day 
// is lower than the price on the preceding day by exactly 1. The first day of the period is exempted from this rule.
// Return the number of smooth descent periods.

// Example 1:
// Input: prices = [3,2,1,4]
// Output: 7
// Explanation: There are 7 smooth descent periods:
// [3], [2], [1], [4], [3,2], [2,1], and [3,2,1]
// Note that a period with one day is a smooth descent period by the definition.
// Example 2:
// Input: prices = [8,6,7,7]
// Output: 4
// Explanation: There are 4 smooth descent periods: [8], [6], [7], and [7]
// Note that [8,6] is not a smooth descent period as 8 - 6 ≠ 1.
// Example 3:
// Input: prices = [1]
// Output: 1
// Explanation: There is 1 smooth descent period: [1]
// Constraints:
// 1 <= prices.length <= 105
// 1 <= prices[i] <= 105

public class Solution {
    public long GetDescentPeriods(int[] prices) {
        int prev = -1;
        long days = 0;
        int contiguous = 0;
        for(int i = 0; i < prices.Length; i++){
            if(prices[i] == prev - 1)
                contiguous++;
            else
                contiguous = 1;
            days += contiguous;
            prev = prices[i];
        }
        return days;
    }
}