First arrivals: Positive proof strip
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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
firstCopies. Keep the first copy of each number inreadings. Skip any later copies of the same number. Keep the order in which the numbers first appear. For [4, 2, 4, 3, 2],firstCopiesis [4, 2, 3]. - Create a list
positiveValuesthat keeps only the numbers infirstCopiesthat are greater than 0, in the same order. - Complete
firstArrivalsPositiveProofStripso it returnspositiveValues. Return it, do not print it.
Example
If readings is [9, -1, 7, 9, 6], then firstCopies is [9, -1, 7, 6] and firstArrivalsPositiveProofStrip returns [9, 7, 6].
Rules
- If no number is greater than 0, return [].
Test data
TEST DATA 1: readings is [16, -6, 3, 0, 3].
TEST DATA 2: readings is [5, 5, 5, -6].
Examples
Input: readings = [16,-6,3,0,3] Output: [16,3]
firstCopies is [16, -6, 3, 0]. Keep only numbers greater than 0, without changing their order. Return [16, 3].
Input: readings = [5,5,5,-6] Output: [5]
firstCopies is [5, -6]. Keep only numbers greater than 0, without changing their order. Return [5].
Input: readings = [] Output: []
firstCopies is []. Keep only numbers greater than 0, without changing their order. Return [].
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 firstCopies 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.