Positive trays: Even-key census
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
kept. Keep only numbers greater than 0 fromreadings. Put them inkeptin their original order. Keep repeated numbers. Leave out 0 and negative numbers. - Count the even numbers in
kept. Store the count inevenCount. A number is even when it divides by 2 with no remainder. - Complete
positiveTraysEvenKeyCensusso it returnsevenCount. Return it, do not print it.
Example
If readings is [11, -7, 9, 4, 9], then kept is [11, 9, 4, 9] and positiveTraysEvenKeyCensus returns 1.
Rules
- If
keptis empty, return 0.
Test data
TEST DATA 1: readings is [8, 0, -10, 8, 19].
TEST DATA 2: readings is [8, 8, -9, 8].
Examples
Input: readings = [8,0,-10,8,19] Output: 2
kept is [8, 8, 19]. The even numbers are [8, 8]. There are 2, so return 2.
Input: readings = [8,8,-9,8] Output: 3
kept is [8, 8, 8]. The even numbers are [8, 8, 8]. There are 3, so return 3.
Input: readings = [] Output: 0
kept is []. The even numbers are []. There are 0, so 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 kept 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.