Multi-dimensional arrays in C++ - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a multi-dimensional array in C++?

A multi-dimensional array is an array of arrays. It allows storing data in a table-like structure with rows and columns, such as a 2D array.

beginner

How do you declare a 2D array with 3 rows and 4 columns in C++?

You declare it like this: int arr[3][4]; This creates 3 rows and 4 columns of integers.

beginner

How do you access the element in the 2nd row and 3rd column of a 2D array named arr?

Use arr[1][2]. Remember, indexing starts at 0, so row 2 is index 1 and column 3 is index 2.

intermediate

How can you initialize a 2D array with values at the time of declaration?

You can write: int arr[2][3] = {{1, 2, 3}, {4, 5, 6}}; This sets the first row to 1,2,3 and the second row to 4,5,6.

intermediate

What happens if you try to access an element outside the bounds of a multi-dimensional array?

Accessing outside the array bounds causes undefined behavior. This can lead to wrong data, crashes, or security issues.

How do you declare a 3D array with dimensions 2x3x4 in C++?

A int arr[2,3,4];

B int arr[3][4][2];

C int arr[2][3][4];

D int arr(2,3,4);

The correct syntax uses square brackets for each dimension: int arr[2][3][4];

What is the index of the first element in any dimension of a C++ array?

A 1

B Depends on the array

C -1

D 0

C++ arrays start indexing at 0 for every dimension.

Which of these is a valid way to access an element in a 2D array named arr?

A arr[2][3]

B arr(2,3)

C arr[2,3]

D arr{2}{3}

Use square brackets for each dimension: arr[2][3].

What does the following code do? <br> int arr[2][2] = {{1, 2}, {3, 4}};

A Causes a syntax error

B Creates a 2x2 array with values 1,2 in first row and 3,4 in second row

C Creates an empty 2D array

D Creates a 1D array with 4 elements

The code initializes a 2x2 array with the given values in each row.

What is the risk of accessing arr[5][5] if arr is declared as int arr[3][3];?

A Undefined behavior, possible crash or wrong data

B Compiler error

C No risk, it returns 0

D It will resize the array automatically

Accessing outside declared bounds causes undefined behavior.

Explain how multi-dimensional arrays are stored in memory in C++ and how indexing works.

Think about how a 2D table is stored as a long list in memory.

Describe how to declare, initialize, and access elements in a 2D array in C++.

Use examples with small arrays to explain.