2D Array Jeopardy

Basics

100

What is a 2D array?

A one dimensional array of arrays, or a table/matrix

200

How do you appropriately declare and initialize a 2D array of integers?

int [][] name = new int[rows][columns]

300

In a 2D array, if array[3][2] = 5;, what does this represent?

The element in the 4th row and 3rd column of the array is 5.

400

What is the default value of a boolean in a 2D array in Java?

False

500

How would you initialize a 3x3 matrix of integers with values 1 through 9?

int[][] matrix = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};

Manipulating 2D Arrays

100

How do you change the value of an element in a 2D array?

By specifying the indices and assigning a new value, e.g., array[1][2] = 5;

200

What function would you use to transpose a matrix in many programming languages?

You’d swap rows and columns, or you could use a custom function to achieve this.

300

Given a 2D array matrix[3][3], how would you set all elements to zero?

for (int i = 0; i < matrix.length; i++) {    

     for (int j = 0; j < matrix[i].length; j++) {                  matrix[i][j] = 0;    

     } 

}

400

What will happen if you attempt to set an element outside the bounds of a 2D array (e.g., array[4][10] in a 3x5 array)?

It will throw an IndexOutOfBoundsException.

500

How do you rotate a square matrix (2D array) 90 degrees clockwise?

Code

Array Traversal

100

How would you traverse a 2D array using a nested for loop?

for (int i = 0; i < arr.length; i++) {    

for (int j = 0; j < arr[i].length; j++) {        System.out.println(arr[i][j]);    

} 

}

200

In a 2D array, how can you traverse all the elements and calculate the sum of all values?

int sum = 0; 

for (int i = 0; i < array.length; i++) {    

     for (int j = 0; j < array[i].length; j++) {                       sum += array[i][j];    

     } 

}

300

What is the time complexity of traversing a 2D array with dimensions M x N?

O(M * N).

400

How would you print the diagonal elements of a square matrix array[n][n]?

for (int i = 0; i < array.length; i++) {    System.out.println(array[i][i]); 

}

500

How would you traverse a 2D array in a spiral order starting from the top-left corner?

Code

Advanced Concepts

100

In a 2D array arr, how can you access the last element in each row using a loop?

for (int i = 0; i < arr.length; i++) {    System.out.println(arr[i][arr[i].length - 1]); }

200

How can you dynamically resize a 2D array?

You can create a new array with a larger size and copy elements from the old array to the new one

300

What is a jagged array in the context of 2D arrays?

A jagged array is an array of arrays where the inner arrays may have different lengths

400

What is the concept of "row-major" and "column-major" ordering in a 2D array?

• Row-major ordering: The elements of each row are stored in consecutive memory locations (e.g., C/C++).
• Column-major ordering: The elements of each column are stored consecutively (e.g., Fortran).

500

How can you implement matrix addition using two 2D arrays?

for (int i = 0; i < rows; i++) {            

     for (int j = 0; j < cols; j++) {                

          result[i][j] = matrix1[i][j] + matrix2[i][j]; 

     }        

}