Neighbor notes: Positive-ink invoice
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
differences. Start at the second number inreadings. Subtract the number just before it from the current number. Repeat for each later number. Put the answers in order. For [5, 8, 2],differencesis [3, -6]. A list with fewer than two numbers gives an emptydifferences. - Add only the numbers in
differencesthat are greater than 0. Store the sum inpositiveTotal. - Complete
neighborNotesPositiveInkInvoiceso it returnspositiveTotal. Return it, do not print it.
Example
If readings is [9, 8, -5, 7, 9], then differences is [-1, -13, 12, 2] and neighborNotesPositiveInkInvoice returns 14.
Rules
- Skip 0 and negative numbers.
- If no number is greater than 0, return 0.
Test data
TEST DATA 1: readings is [0, 15, 15, 10, -6].
TEST DATA 2: readings is [4, 4, -4, 4].
Examples
Input: readings = [0,15,15,10,-6] Output: 15
differences is [15, 0, -5, -16]. Keep [15] and add those numbers. Return 15.
Input: readings = [4,4,-4,4] Output: 8
differences is [0, -8, 8]. Keep [8] and add those numbers. Return 8.
Input: readings = [] Output: 0
differences 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); 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 differences 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.