AP CSA Unit 4 Day 27: 2D Array Edge Elements
Share
Unit 4, Data Collections • Cycle 2
Day 27 Advanced Practice • Harder Difficulty
Focus: 2D Array Edge Elements
Hard
2D Array Edge Elements
Advanced Practice Question
Format: 2D Array Edge Elements
What is the output?
What is the output?
int[][] grid = {
{1, 2, 3},
{4, 5, 6},
{7, 8, 9}
};
int count = 0;
for (int r = 0; r < grid.length; r++) {
for (int c = 0; c < grid[r].length; c++) {
if (r == 0 || r == grid.length - 1 ||
c == 0 || c == grid[r].length - 1) {
count++;
}
}
}
System.out.println(count);
Difficulty: Hard |
Topic: 2D Array Edge Elements |
Cycle: 2 (Advanced)
Why This Answer?
Edge elements are in first/last row OR first/last column. Top row: 3, bottom row: 3, left column middle: 1, right column middle: 1. Total = 3+3+1+1 = 8 (corners counted once).
Common Mistake
Watch Out!
Double-counting corner elements or missing middle edge elements.
AP Exam Strategy
Edge check: r==0 OR r==last OR c==0 OR c==last (OR not AND).
Master This Topic
This Cycle 2 HARD question tests 2d array edge elements. Review Unit 4 concepts to build mastery of data collections.
- Understanding 2d array edge elements
- Tracing code execution accurately
- Avoiding common pitfalls
Ready for More Challenges?
Cycle 2 questions prepare you for the hardest AP CSA exam questions.
Study Games Practice FRQs