AP Computer Science A Unit 2 Cheatsheet: Selection and Iteration

Three core components:

• Sequencing: statements execute in order
• Selection: choice based on true/false condition
• Repetition: process repeats until outcome reached

Order matters—changing the sequence of statements, where a selection (if) is placed, or a loop's condition can change the algorithm's result, so trace the code carefully (though some changes, like reordering independent statements, leave the result the same).

Precedence: ! → && → ||

Short-circuit: && and || stop evaluating once result is determined.

Three parts:

1. Initialization: executed once before first evaluation
2. Boolean expression: evaluated before each iteration
3. Update: executed after body, before next evaluation

Loop control variable: initialized in part 1, typically incremented in part 3.

Equivalence: any for loop can be rewritten as while loop (and vice versa).

Trace execution order: init → test → body → update → test → …