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2019 AP CS Exam Free Response Solutions

AP Computer Science Practice Problems & Resources by Topic

Each section focuses on an AP Computer Science Exam topic that has been tested extensively on previous exams.
All problems were created by AP CS Tutor Brandon Horn of, Inc.

Featured Practice Problems – Droppy & Mazer

  • Traverse a 2D array in a non-trivial order (like the AP CS Pictures Lab)
  • Manipulate String objects (like the AP CS Magpie Lab)

Try the Droppy Free Response Practice Problem
Try the Mazer Free Response Practice Problem

Inheritance & Polymorphism

  • Design and implement subclasses
  • Override superclass methods
  • Work with abstract classes and methods

See the Inheritance & Polymorphism Practice Problems

2D Arrays

  • Traverse a 2D array in row-major order
  • Fill a two dimensional array
  • Visit specific elements of a 2 dimensional array

See the 2D Array Practice Problems


  • Trace recursive methods
  • Implement recursive methods
  • Determine the purpose of recursive methods

See the Recursion Practice Problems
See the Recursive Method Tracing Technique

Lists & ArrayLists

  • Compare consecutive elements of a List
  • Remove specific elements from a List
  • Find the maximum in an ArrayList

See the List & ArrayList Practice Problems

Sorting & Searching

  • Code selection sort, insertion sort and merge sort
  • Identify and complete variants (ex: back to front)
  • Determine if an implementation is correct

Try the Sorting & Searching Practice Problems

GridWorld: The AP Computer Science Case Study

Note: GridWorld will not be featured on the 2015 and subsequent AP CS Exams.

  • Practice with Location and Grid
  • Write a complete subclass of Critter
  • Use Grid to implement a game

See the GridWorld Case Study Practice Problems
See the GridWorld Case Study Explanations
See the GridWorld Case Study Solutions

Additional Practice Problems by Topic

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Solutions to AP Computer Science Exam Problems