2D Arrays Practice Questions
AP (Advanced Placement) · AP Computer Science A · 150 free MCQs with instant results and detailed explanations.
150
Total
50
Easy
80
Medium
20
Hard
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Sample Questions from 2D Arrays
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Q1
Easy
What is the primary purpose of a 2D array in programming?
A.
To store data in a tabular format
B.
To perform mathematical calculations
C.
To create graphical user interfaces
D.
To manage user input
Show Answer & Explanation
Correct Answer: A
A 2D array is primarily used to store data in a tabular format, allowing for the organization of data in rows and columns, which is essential for various applications such as matrix operations and grid layouts.
Q2
Easy
Given the following 2D array: int[][] arr = {{1, 2}, {3, 4}, {5, 6}}; What is the value of arr[1][0]?
A.
2
B.
3
C.
4
D.
5
Show Answer & Explanation
Correct Answer: B
In the 2D array, arr[1][0] refers to the element at the second row (index 1) and the first column (index 0), which is 3.
Q3
Easy
If you need to iterate through a 2D array to find the sum of all its elements, what kind of loop structure is most suitable?
A.
A single for loop
B.
A nested for loop
C.
A while loop only
D.
A do-while loop only
Show Answer & Explanation
Correct Answer: B
A nested for loop is most suitable for iterating through a 2D array because it allows you to loop through each row and each column within those rows to access every element.
Q4
Medium
Given a 2D array named 'matrix' of size 3x3, which of the following statements correctly accesses the element in the second row and first column?
A.
matrix[1][0]
B.
matrix[2][1]
C.
matrix[0][1]
D.
matrix[1][1]
Show Answer & Explanation
Correct Answer: A
In a 2D array, indexing starts at 0. Therefore, the second row is indexed by 1, and the first column is indexed by 0, making matrix[1][0] the correct access.
Q5
Medium
How many elements are in a 2D array defined as 'int[][] nums = new int[4][5];'?
A.
9
B.
20
C.
15
D.
4
Show Answer & Explanation
Correct Answer: B
A 2D array with dimensions 4 and 5 contains 4 rows and 5 columns, which gives a total of 4 * 5 = 20 elements.
Q6
Medium
In a 2D array, if 'matrix[0][0]' is set to 5 and 'matrix[1][1]' is set to 10, what will 'matrix[1][0] + matrix[0][1]' evaluate to given that all other elements are initialized to 0?
A.
5
B.
10
C.
15
D.
0
Show Answer & Explanation
Correct Answer: D
Since 'matrix[0][1]' and 'matrix[1][0]' are initialized to 0, the sum will be 0 + 0 = 0.
Q7
Medium
Which of the following methods is suitable for finding the maximum value in a 2D array named 'grid'?
A.
int max = grid[0][0]; for(int[] row : grid) { for(int val : row) { if(val > max) max = val; }}
B.
int max = 0; for(int i = 0; i < grid.length; i++) { for(int j = 0; j < grid[i].length; j++) { if(grid[i][j] > max) max = grid[i][j]; }}
C.
int max = Integer.MIN_VALUE; for(int[] row : grid) { for(int val : row) { max = Math.max(max, val); }}
D.
All of the above
Show Answer & Explanation
Correct Answer: D
All provided methods correctly iterate through the 2D array to find the maximum value, thus any of them can be used.
Q8
Hard
Given a 2D array 'matrix' of size 3x3. If 'matrix[1][2]' is updated to 10, what will be the value of 'matrix[1][2]' after this operation?
A.
10
B.
The original value of matrix[1][2]
C.
0
D.
Null
Show Answer & Explanation
Correct Answer: A
'matrix[1][2]' is directly updated to 10. Hence, after the operation, its value will be 10.
Q9
Hard
In a 2D array 'grid' representing a chessboard, how would you access the piece located at the 4th row and 5th column using Java syntax?
A.
grid[4][5]
B.
grid[3][4]
C.
grid[5][4]
D.
grid[4,5]
Show Answer & Explanation
Correct Answer: B
In Java, array indexing starts at 0. Therefore, the 4th row and 5th column corresponds to indices [3][4].
Q10
Hard
In a 2D array 'matrix' defined as int[][] matrix = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}}; what will matrix[1][2] return?
A.
6
B.
5
C.
7
D.
8
Show Answer & Explanation
Correct Answer: A
matrix[1][2] accesses the element in the second row (index 1) and the third column (index 2) of the array, which is 6.
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2D Arrays — AP (Advanced Placement) AP Computer Science A Practice Questions Online
This page contains 150 practice MCQs for the chapter 2D Arrays in AP (Advanced Placement) AP Computer Science A. The questions are organized by difficulty — 50 easy, 80 medium, 20 hard — so you can choose the right level for your preparation.
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