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- Iteration statements (loops) change the flow of control by repeating a set of statements zero or more times until a condition is met.
- Loops often have a loop control variable that is used in the Boolean condition, requiring the steps of initializing, testing, and changing the loop variable.
- In while loops, the Boolean expression is evaluated before each iteration, and the loop body executes as long as the condition is true, stopping when the condition is false.
- If the Boolean expression in a while loop evaluates to false initially, the loop body is not executed at all.
- Infinite loops occur when the Boolean expression always evaluates to true, causing the loop to never end.
- Off-by-one errors happen when the iteration statement loops one time too many or too few.
- Input-controlled loops often use a sentinel value (e.g., "bye" or -1) provided by the user to signal the loop to stop, though these are not on the AP CSA exam.
- Standard algorithms like computing a sum or average are commonly implemented with loops.
- In a for loop, the initialization statement is only executed once before the evaluation of the test Boolean expression. The variable being initialized is referred to as a loop control variable.
- In each iteration of a for loop, the increment or decrement statement is executed after the entire loop body is executed and before the Boolean expression is evaluated again.
- A for loop can be rewritten into an equivalent while loop and vice versa.
- Loops can be used to traverse or process a string.
- Standard algorithms using string traversals can determine if one or more substrings have a particular property.
- Loops can calculate the number of substrings that meet specific criteria.
- String traversals can create a new string with the characters reversed.
- Nested iteration statements are iteration statements that appear in the body of another iteration statement.
- When a loop is nested inside another loop, the inner loop must complete all its iterations before the outer loop can continue.
- A trace table can be used to keep track of the variables and their values throughout each iteration of the loop.
- We can determine the number of times a code segment will execute with a statement execution count. This is called run-time analysis.
- The number of times a loop executes can be calculated by largestValue - smallestValue + 1, where these are the largest and smallest values of the loop counter variable possible in the body of the loop.
- The number of times a nested for-loop runs is the number of times the outer loop runs times the number of times the inner loop runs.
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