.NET OA: 3^x * 5^y Count and Decreasing Subarrays

Requirements

Task 1:

• Given an inclusive interval, determine how many values within it have the form 3^x * 5^y.
• Build the possible values without allowing arithmetic overflow.

Input: lo = 1, hi = 80

Output: 9

Explanation: The valid numbers are 1, 3, 5, 9, 15, 25, 27, 45, 75; 81 exceeds the upper bound, so this example produces 9 valid values.

Task 2:

• You are given an array of integers.
• Count every contiguous subarray with at least two elements for which each element is exactly one less than the element immediately before it.

def count_decreasing_subarrays(arr: list[int]) -> int:

The function returns the count as an integer.

Input: arr = [8, 7, 6, 4, 3, 10]

Output: 4

Explanation: The run [8, 7, 6] supplies three qualifying subarrays, and [4, 3] adds one more.

Input: arr = [5, 4, 3, 2]

Output: 6

Explanation: All subarrays of length two or greater from this four-element decreasing-by-one run qualify: 4 * 3 / 2 = 6.