AP CSA FRQ Guide
2012 FRQ 3: HorseBarn
Find the index of a named horse in a barn array and consolidate horses toward the front while preserving order.
Array Search and Compaction22 minute targetarraysobjectsnullscompaction
Skills Tested
What this FRQ is really practicing
arraysobjectsnullscompaction
Review these topics before attempting the problem.
Starter Approach
How to begin with your own plan
- 1Search through an array that may contain null entries.
- 2Move non-null horse references to earlier spaces without changing their relative order.
Attempt the problem before opening the solution.
Common Mistakes
Mistakes to watch for while writing
Calling getName on null spaces.
Changing the relative order of horses during consolidation.
Leaving duplicate horse references after moving them forward.
Self Check
Review questions before you submit
Searches safely around null barn spaces.
Check for null before calling methods on a horse.
Returns -1 when the horse is not found.
Return -1 after the full search.
Uses a target index for compaction.
A separate write index keeps order cleanly.
Sets remaining spaces to null after consolidation.
Old references at the end must be cleared.
Practice Links