AP Computer Science P Unit 3 Cheatsheet: Algorithms and Programming

Variable: Named storage holding one value at a time (can be a list or collection).

• Use meaningful names for readability
• Types: numbers, Booleans, lists, strings
• Assignment operator: a ← expression
• Most recent assignment is the current value
• Example: a ← 1, b ← a, a ← 2 → b still equals 1

Procedure: A named group of programming instructions that may have zero or more parameters (inputs) and may or may not return a value.

Call syntax: procName(arg1, arg2, ...)

Definition:

• PROCEDURE procName(parameter1, parameter2, ...) { statements }
• RETURN(expression) — returns value and exits

Built-in procedures:

• DISPLAY(expression) — output value
• INPUT() — accept user input

Procedural abstraction: Hides implementation; enables code reuse, modularity, and complexity management. Parameters generalize procedures for different inputs.

Algorithm: Finite set of instructions to accomplish a task. Built from sequencing, selection, and iteration.

Expressing algorithms: Natural language, diagrams, pseudocode, or code.

Comparing algorithms: Different algorithms can solve the same problem; some are more efficient. Equivalent algorithms may have different side effects.

Building blocks: Max/min, sum/average, divisibility, pathfinding. Reusing correct algorithms reduces development time and errors.

Efficiency: Measured by computational resources (time/space) as function of input size. Polynomial time (constant, linear, quadratic, cubic) = reasonable. Exponential/factorial = unreasonable.

Heuristic: Produces good (not guaranteed optimal) solution when exact algorithms are impractical.