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

A Calgary .NET engineer OA contains two easy coding tasks: count numbers of the form `3^x * 5^y` in a range, and count subarrays of length at least two where each next element is one less than the previous. Requirements Task 1: Count how many numbers in a given range can be represented as 3^x * 5^y. Generate candidates carefully and avoid overflow. Task 2: Input: an integer array. Count subarrays of length at least 2 satisfying arr[i] = arr[i - 1] - 1 for every adjacent pair in the subarray. Notes For task 1, nested generation over powers of 3 and 5 is enough when overflow guards are correct. For task 2, scan maximal runs where every adjacent difference is -1. A run of length L contributes L * (L - 1) / 2 qualifying subarrays of length at least two. Preparation For the power-count task, generate powers with division-based overflow guards such as while x <= hi // 3 and deduplicate candidates in a set before range counting. For the decreasing-subarray task, practise deriving the run formula: every maximal run of length L contributes all choices of start/end with length at least two, L * (L - 1) / 2.