Expanding panels: Even-key census
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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
shortestLengths. All numbers inreadingsare 0 or greater. For each position, find the shortest group that ends at that position and has a sum of at leastk. The group must contain at least one number, and its numbers must be next to each other. Record the length of that group. Record 0 if no such group exists. Put one answer per position inshortestLengths. - Count the even numbers in
shortestLengths. Store the count inevenCount. A number is even when it divides by 2 with no remainder. - Complete
expandingPanelsEvenKeyCensusso it returnsevenCount. Return it, do not print it.
Example
If readings is [1, 4, 3, 8, 3] and k is 8, then shortestLengths is [0, 0, 3, 1, 2] and expandingPanelsEvenKeyCensus returns 3.
Rules
- 0 counts as an even number.
- If
shortestLengthsis empty, return 0. k(a whole number from 1 to 8) is the sum each group in task 1 must reach.
Test data
TEST DATA 1: readings is [18, 4, 0, 5, 18] and k is 8.
TEST DATA 2: readings is [9, 9, 9, 6] and k is 7.
Examples
Input: readings = [18,4,0,5,18] k = 8 Output: 1
shortestLengths is [1, 2, 3, 3, 1]. The even numbers are [2]. There are 1, so return 1.
Input: readings = [9,9,9,6] k = 7 Output: 1
shortestLengths is [1, 1, 1, 2]. The even numbers are [2]. There are 1, so return 1.
Input: readings = [] k = 1 Output: 0
shortestLengths is []. The even numbers are []. There are 0, so return 0.
Input limits
- 0 <= input size <= 64.
- k is a whole number from 1 to 8. Answers fit in a signed 32-bit integer: -2,147,483,648 through 2,147,483,647.
- Input numbers are whole numbers from 0 through 20.
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 shortestLengths 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.