Multi-dimensional arrays in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a 2D array element access

What is the output of this C# code snippet?

C Sharp (C#)

int[,] matrix = { {1, 2, 3}, {4, 5, 6} };
Console.WriteLine(matrix[1, 2]);

A Runtime error

B 5

C 3

D 6

💡 Hint

Remember that the first index is the row and the second is the column.

The matrix has two rows and three columns. matrix[1, 2] accesses the element in the second row and third column, which is 6.

❓ Predict Output

intermediate

Length properties of a 3D array

Given the following 3D array, what is the output of the code below?

C Sharp (C#)

int[,,] cube = new int[2,3,4];
Console.WriteLine(cube.GetLength(1));

A 3

B 2

C 4

D Runtime error

💡 Hint

GetLength(n) returns the size of the dimension n, starting from 0.

The array has dimensions 2 (dim 0), 3 (dim 1), and 4 (dim 2). cube.GetLength(1) returns 3.

🔧 Debug

advanced

Identify the error in multi-dimensional array initialization

What error will this code produce when compiled or run?

C Sharp (C#)

int[,] grid = new int[2, 2] { {1, 2}, {3, 4}, {5, 6} };

A Compile-time error: Too many initializers for the array

B Runtime error: Index out of range

C No error, compiles and runs fine

D Compile-time error: Missing semicolon

💡 Hint

Check the declared size versus the number of initializer rows.

The array is declared with size 2x2 but initialized with 3 rows, which causes a compile-time error.

❓ Predict Output

advanced

Output of nested loops over a 2D array

What will be printed by this code?

C Sharp (C#)

int[,] arr = { {1, 2}, {3, 4} };
for (int i = 0; i < arr.GetLength(0); i++)
{
    for (int j = 0; j < arr.GetLength(1); j++)
    {
        Console.Write(arr[i, j] + " ");
    }
    Console.WriteLine();
}

A 1 3 \n2 4 \n

B 1 2 3 4 \n

C 1 2 \n3 4 \n

D Runtime error

💡 Hint

The outer loop iterates rows, inner loop iterates columns.

The code prints each row's elements separated by spaces, then a newline after each row.

🧠 Conceptual

expert

Memory layout of multi-dimensional arrays in C#

Which statement best describes how multi-dimensional arrays are stored in memory in C#?

A Multi-dimensional arrays are stored as arrays of arrays (jagged arrays) with separate memory blocks for each sub-array.

B Multi-dimensional arrays are stored as a single contiguous block of memory in row-major order.

C Multi-dimensional arrays are stored in column-major order similar to Fortran arrays.

D Multi-dimensional arrays are stored randomly in memory without any specific order.

💡 Hint

Think about how C# handles rectangular arrays compared to jagged arrays.

C# rectangular multi-dimensional arrays are stored as a single contiguous block in row-major order, meaning rows are stored one after another.