Recursive shelves: Positive-ink invoice
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Inputs
readings is a list of integers (numbers with no decimal part). It may be empty, and numbers may repeat unless task 1 says otherwise.
Your tasks
- Create a list
sectionSums. Start with the wholereadingslist as a section. Record the sum of that section. If it has more than one number, split it into a left half and a right half. Use the same steps on the left half first, then on the right half. When a section has an odd length, the left half has one fewer number. A section with one number is not split. Do not record empty sections.sectionSumscontains the sums in the order you record them. - Add only the numbers in
sectionSumsthat are greater than 0. Store the sum inpositiveTotal. - Complete
recursiveShelvesPositiveInkInvoiceso it returnspositiveTotal. Return it, do not print it.
Example
If readings is [2, 2, 4, -1, 2], then sectionSums is [9, 4, 2, 2, 5, 4, 1, -1, 2] and recursiveShelvesPositiveInkInvoice returns 29.
Rules
- Skip 0 and negative numbers.
- If no number is greater than 0, return 0.
Test data
TEST DATA 1: readings is [-7, 6, 9, 6, 0].
TEST DATA 2: readings is [9, -9, 9, 9].
Examples
Input: readings = [-7,6,9,6,0] Output: 56
sectionSums is [14, -1, -7, 6, 15, 9, 6, 6, 0]. Keep [14, 6, 15, 9, 6, 6] and add those numbers. Return 56.
Input: readings = [9,-9,9,9] Output: 63
sectionSums is [18, 0, 9, -9, 18, 9, 9]. Keep [18, 9, 18, 9, 9] and add those numbers. Return 63.
Input: readings = [] Output: 0
sectionSums is []. Keep [] and add those numbers. Return 0.
Input limits
- 0 <= input size <= 64.
- Answers fit in a signed 32-bit integer: -2,147,483,648 through 2,147,483,647.
- Input numbers have no decimal part. They range from -1,000,000 to 1,000,000. Follow any extra input rules in task 1.
Efficiency goal
Big-O describes how the work or memory needed grows as the input gets larger.
Efficiency goal: time O(n log n); extra memory, including the helper list, O(n). n is the input length. These labels describe how work and memory grow with the input.
Practice focus
Build sectionSums first, then return exactly what the tasks ask for. Follow the order, keep repeated values when the rule says so, and check the empty case.