Written Response 2: Algorithms, errors and testing, and abstraction
Crowdsourced pothole reports
- Units 3 and 5
- 3 points
- About 45 minutes
Three prompts about the program's code. (a) Algorithm development: explain how a loop or condition works, such as how many times a loop runs or what makes it stop. (b) Errors and testing: describe a call, input or change that causes an error or wrong behavior and explain why. (c) Data and procedural abstraction: explain how the list or procedure manages complexity, or explain, step by step, an algorithm that uses the list. On the exam: Question 2 of 2 (3 points: parts (a), (b) and (c) are worth 1 point each). Section II has 2 written-response questions (4 prompts) in 60 minutes, taken in Bluebook at the end-of-course exam; no calculator. On the real exam the questions are about your own Create performance task program, and you can see your Personalized Project Reference (screenshots of your procedure and list code). The Create task is 30% of the AP score, scored on 6 one-point rows: video, program requirements, WR1, WR2(a), WR2(b) and WR2(c). On this site you answer the same kinds of prompts about a short sample program given with the question.
The question and its sources
Answer parts (a), (b) and (c) about the sample program below. On the exam these prompts are about your own Create task program and your Personalized Project Reference; here, the code segments below play that role. Refer to the specific code in every answer, and write in complete sentences.
About the program
A city app lets residents report potholes. Each report is the street name, typed by the resident. The city's crew repairs any street with at least 3 reports. The program reads reports until a staff member types done, then displays each street on the crew's list that needs repair.
Example: the 8 reports Main St, Oak Ave, Main St, Elm St, Main St, Oak Ave, Elm St and Oak Ave display Oak Ave Main St.
Source: Sample program written for this practice question (hypothetical)
Procedure: needsRepair
PROCEDURE needsRepair(reports, street, threshold)
{
count ← 0
FOR EACH r IN reports
{
IF(r = street)
{
count ← count + 1
}
}
IF(count ≥ threshold)
{
RETURN(true)
}
RETURN(false)
}Source: Sample program written for this practice question (hypothetical)
List: storing the reports in reports
reports ← []
newReport ← INPUT()
REPEAT UNTIL(newReport = "done")
{
APPEND(reports, newReport)
newReport ← INPUT()
}Source: Sample program written for this practice question (hypothetical)
Calling the procedure and using the list
streets ← ["Oak Ave", "Main St", "Elm St"]
FOR EACH s IN streets
{
IF(needsRepair(reports, s, 3))
{
DISPLAY(s)
}
}Source: Sample program written for this practice question (hypothetical)
Suggested time: 45 minutes
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Part (a)
1 pointIdentify the number of times the body of the iteration statement in needsRepair executes during one run of the program with the 8 example reports. Explain how you got your answer.
0 / 2,500 characters
Part (b)
1 pointWrite a call to needsRepair with specific argument(s) that the procedure accepts but that cause it to behave incorrectly. Describe the incorrect behavior, and explain why it happens as a result of your call. If no call with accepted arguments can make needsRepair behave incorrectly, explain why.
0 / 2,500 characters
Part (c)
1 pointSuppose you are given a procedure cleanName(name) that returns a standard form of a street name: it removes extra spaces, ignores capitalization, and shortens "Street" to "St" and "Avenue" to "Ave". Explain in detailed steps how to use cleanName with the list reports to count the reports for a street so that different ways of typing the same street are counted together. Your explanation must be detailed enough for someone else to write the program code.
0 / 2,500 characters
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