Unit 4 Cycle 2 Day 5: 2D Array Initialization
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Unit 4, Data Collections • Cycle 2
Day 5 Advanced Practice • Harder Difficulty
Focus: 2D Array Initialization
Hard
2D Array Initialization
Advanced Practice Question
Format: 2D Array Initialization
What is the output?
What is the output?
int[][] matrix = new int[3][4];
matrix[0][0] = 1;
matrix[2][3] = 9;
int count = 0;
for (int r = 0; r < matrix.length; r++) {
for (int c = 0; c < matrix[r].length; c++) {
if (matrix[r][c] == 0) {
count++;
}
}
}
System.out.println(count);
Difficulty: Hard |
Topic: 2D Array Initialization |
Cycle: 2 (Advanced)
Why This Answer?
Array has 3 rows × 4 columns = 12 total elements. Two are set to non-zero (1 and 9), leaving 12 - 2 = 10 elements at default value 0.
Common Mistake
Watch Out!
Forgetting that 2D arrays auto-initialize all elements to 0, or miscounting total elements.
AP Exam Strategy
2D array size = rows × columns. New arrays auto-initialize: int→0, double→0.0, boolean→false, objects→null.
Master This Topic
This Cycle 2 HARD question tests 2d array initialization. Review Unit 4 concepts to build mastery of data collections.
- Understanding 2d array initialization
- Tracing code execution accurately
- Avoiding common pitfalls
Ready for More Challenges?
Cycle 2 questions prepare you for the hardest AP CSA exam questions.
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