AP · Analysis & Prediction

2024 AP AP Computer Science A Past Paper: Analysis & Answers

The 2024 AP Computer Science A Free-Response section consisted of 4 standard 9-point questions totaling 36 marks across 90 minutes. It covered methods and control structures with random simulation (Q1), class design with multi-variable state tracking (Q2), ArrayList and String manipulations with prefix filtering (Q3), and a challenging 2D array non-standard path traversal (Q4). The chief reader report indicates that Question 4 (mean 3.20) and Question 3 (mean 4.33) presented significant algorithmic hurdles, specifically around off-by-one errors, 2D array boundary logic, and String prefix processing.

Updated: 18 Aug 2026

Analysis Sample paper

Difficulty 3.4/5

Total marks

Duration

90 mins

Most tested

Data Collections (ArrayList & 2D Arrays)

Paper breakdown

Section II: Free Response: 36 marks · 90 mins

Top chapters

Unit 4: Data Collections (Course Content) · 18 marksUnit 2: Selection and Iteration (Course Content) · 9 marksUnit 3: Class Creation (Course Content) · 9 marks

Executive Overview & Difficulty Verdict

The 2024 AP Computer Science A FRQ paper follows the canonical 4-question, 36-mark blueprint. The global mean was 3.18, with FRQ question averages ranging from a high of 5.70/9 on Question 2 (Class Design) to a low of 3.20/9 on Question 4 (2D Array Pathfinding). Overall, the paper represents a moderate-to-challenging assessment, heavily weighting algorithmic control flow, robust edge-case handling, and multi-object coordination.

Where the Marks Are Won and Lost

Question 1 (Methods & Control Structures - Feeder): Scored an average of 4.83/9. The most common mark drops came from generating random integers in the range \([10, 50]\) using (int)(Math.random() * 41) + 10 (only ~33% got this completely right) and failing to guard against currentFood going negative.
Question 2 (Class Design - Scoreboard): The highest-scoring problem (5.70/9). Students excelled at method and class headers, but lost marks by failing to toggle the active team properly or declaring instance variables inside constructors/methods.
Question 3 (Data Collections / ArrayList & String - WordChecker): Scored 4.33/9. A major stumbling block was searching for prefix occurrences without bounds checking when using substring, or misinterpreting indexOf(target) == 0.
Question 4 (2D Arrays - GridPath): The toughest question (3.20/9). Implementing a non-traditional dynamic pathfinding traversal using a while loop proved difficult; only ~12.5% of students correctly formulated the loop condition and state-update logic without bounds violations or off-by-one fencepost errors.

Key Examiner Pitfalls to Avoid

Chief reader commentary highlights persistent errors: treating void methods as value-returning, comparing Strings with == instead of .equals(), confusing array notation [] with ArrayList .get(), and assuming out-of-bounds 2D array accesses return null rather than throwing an ArrayIndexOutOfBoundsException.

Strategic Revision & Predictions

Focus practice on non-standard loop structures (especially while-loop traversals over 2D grids), rigorous String parsing via indexOf, and probability scaling with Math.random().

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Charts

Marks by chapter

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Question type mix

Compare the mark share of each paper section and question type.

Methods and Control Structures9 marks · 1 questions
Class Design9 marks · 1 questions
ArrayList / 1D Data Manipulation9 marks · 1 questions
2D Array Traversal & Algorithm9 marks · 1 questions

Mark accessibility

Estimate which marks were basic, mid-level, or high-difficulty.

75%within easy or medium reach

easy: 14 marksmedium: 13 markshard: 9 marks

Difficulty trend

Compare difficulty across recent years.

Command word frequency

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Skill weighting

Shows the skill mix this paper tested most heavily.

Study ROI

Bigger bubbles recur more often; higher bubbles carry more marks, helping you rank revision priorities.

Class Design & Encapsulation

9 marks · Difficulty 2.2 · recurrence 100%

ArrayList Traversal & Filtering

9 marks · Difficulty 3.2 · recurrence 100%

Methods, Math.random(), and Conditionals

9 marks · Difficulty 3.3 · recurrence 100%

2D Array Boundary Checking & Path Traversals

9 marks · Difficulty 4.5 · recurrence 100%

Time vs marks

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marksmins

Next-year prediction

Topics worth watching next year, with the reason shown directly below each bar.

String Parsing and List Mutation90%

ArrayList creation and element removal/filtering remains a permanent core anchor of Question 3.

2D Array Row-Major / Column-Major Transformations85%

Following the complex non-standard path traversal in 2024, standard nested loop matrix transformations or row/col swaps are expected to return.

Inheritance and Polymorphism (Class Design variants)75%

Q2 in 2024 tested standalone class design. Subclassing (`extends`) and constructor chaining (`super`) remain highly tested alternatives in the AP rotation.

Cumulative marks ladder

The line is your running mark total question by question; dashed lines are the estimated grade cut-offs. See which question the line crosses your target grade at, so you know how far you must answer cleanly and which questions decide a band.

Topic-year heatmap

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May 2023

May 2024

Unit 4: Data Collections (Course Content)

Unit 3: Class Creation (Course Content)

Unit 2: Selection and Iteration (Course Content)

Examiner insights

Official report

Common pitfalls

Incorrect Math.random() scaling: using `(int)Math.random() * 41` (which truncates before multiplying) or using incorrect range multipliers such as 40 or 50 instead of `(int)(Math.random() * 41) + 10`.
Improper String matching: attempting to use `substring` without verifying if string length is at least target length, causing StringIndexOutOfBoundsException.
2D Array boundary confusion: assuming accessing out-of-bounds indices returns null rather than throwing ArrayIndexOutOfBoundsException.
Loop termination in 2D traversal: using `&&` instead of `||` for continuation conditions, terminating the traversal prematurely before reaching the bottom-right corner.
Off-by-one errors when processing adjacent elements in ArrayLists, leading to IndexOutOfBoundsException at `i - 1` or `i + 1`.

Misconceptions

Believing that `Math.random(n)` accepts a parameter in standard Java syntax.
Assuming instance variables should be re-declared inside method bodies or constructors, turning them into local variables.
Believing a void method (e.g. `simulateOneDay`) returns a status value, or printing output with `System.out.println` instead of using a `return` statement.
Modifying a parameter list alias directly instead of instantiating a new ArrayList, causing unintentional side-effects / data destruction.

Where marks are lost

Failing to account for fencepost items in running sums (omitting the first or last grid cell in Q4b sumPath).
Failing to guard against negative food supplies in Q1a, leaving `currentFood` < 0.
State toggling errors in Q2 when the play score was 0, resulting in resetting both teams or failing to switch back and forth.

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