AP CSP Practice: FOR EACH Loops & List Traversal
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Big Idea 3: Algorithms and Programming
Day 4 Practice • AP CSP Daily Question
🎯 Focus: Loops and Lists
Practice Question
Consider the following code segment:
myList ← [3, 7, 2, 9, 5]
sum ← 0
FOR EACH item IN myList
{
IF (item > 4)
{
sum ← sum + item
}
}
DISPLAY(sum)What value is displayed as a result of executing this code segment?
What This Tests: Big Idea 3 covers list traversals and conditional logic. This question combines a FOR EACH loop with an IF statement to filter which items get processed.
Step-by-Step Trace
| Iteration | item | item > 4? | sum |
|---|---|---|---|
| Start | — | — | 0 |
| 1 | 3 | No | 0 |
| 2 | 7 | Yes | 0 + 7 = 7 |
| 3 | 2 | No | 7 |
| 4 | 9 | Yes | 7 + 9 = 16 |
| 5 | 5 | Yes | 16 + 5 = 21 |
Only items greater than 4 are added: 7 + 9 + 5 = 21
Understanding FOR EACH
The FOR EACH loop visits every element in the list, one at a time:
FOR EACH item IN myList
// item takes on each value: 3, then 7, then 2, then 9, then 5The IF condition acts as a filter—only items that pass the condition (> 4) get added to sum.
Common Mistakes
Mistake: Answer C (26) - Adding all elements
If you got 26, you added ALL elements (3+7+2+9+5). The IF statement filters—only elements greater than 4 should be added.
Mistake: Forgetting 5 is greater than 4
5 > 4 is TRUE, so 5 gets added. Items equal to 4 would NOT be added (the condition is >, not >=).
💡 AP Exam Tip
When tracing loops with conditions, make a table with columns for: iteration number, current item, whether the condition is true, and running totals. This prevents skipping items or miscounting.
Difficulty: Medium • Time: 2-3 minutes • Topic: 3.6 Conditionals & 3.8 Iteration
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