Prefix stencils: Peak ticket
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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
rangeSums. For each position inreadings, add the current number and up tok- 1 numbers just before it. Stop at the start of the input if needed. Record each sum, from left to right. Forreadings= [2, 3, 4] andk= 2,rangeSumsis [2, 5, 7]. - Find the largest number in
rangeSums. Store it inlargest. - Complete
prefixStencilsPeakTicketso it returnslargest. Return it, do not print it.
Example
If readings is [1, 4, 4, 11, -4] and k is 8, then rangeSums is [1, 5, 9, 20, 16] and prefixStencilsPeakTicket returns 20.
Rules
- If
rangeSumsis empty, return 0. - If every number is negative, return the largest negative number. Do not replace it with 0.
k(a whole number from 1 to 8) is the most numbers each sum in task 1 may include.
Test data
TEST DATA 1: readings is [4, 18, -1, 18, 0] and k is 4.
TEST DATA 2: readings is [9, 9, 9, -9] and k is 7.
Examples
Input: readings = [4,18,-1,18,0] k = 4 Output: 39
rangeSums is [4, 22, 21, 39, 35]. The largest number is 39. Return 39.
Input: readings = [9,9,9,-9] k = 7 Output: 27
rangeSums is [9, 18, 27, 18]. The largest number is 27. Return 27.
Input: readings = [] k = 2 Output: 0
rangeSums is []. The list is empty, so return 0.
Input limits
- 0 <= input size <= 50000.
- 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 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 rangeSums 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.