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C Sharp (C#)programming~30 mins

Multi-dimensional arrays in C Sharp (C#) - Mini Project: Build & Apply

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Working with Multi-dimensional Arrays in C#
📖 Scenario: Imagine you are organizing seats in a small movie theater. The theater has rows and columns of seats. You want to keep track of which seats are taken and which are free.
🎯 Goal: You will create a multi-dimensional array to represent the seats, mark some seats as taken, and then print the seating arrangement.
📋 What You'll Learn
Create a 2D array called seats with 3 rows and 4 columns
Use string values: "Free" or "Taken" to mark seats
Mark specific seats as taken using row and column indexes
Print the seating arrangement row by row
💡 Why This Matters
🌍 Real World
Multi-dimensional arrays are useful to represent grids, tables, or layouts like seating charts, game boards, or pixel maps.
💼 Career
Understanding multi-dimensional arrays helps in software development tasks involving data organization, UI layouts, and simulations.
Progress0 / 4 steps
1
Create a 3x4 multi-dimensional array
Create a 2D string array called seats with 3 rows and 4 columns. Initialize all seats with the value "Free".
C Sharp (C#)
Hint

Use string[,] seats = new string[3, 4] and initialize each row with 4 "Free" strings.

2
Mark some seats as taken
Change the seat at row 0, column 1 and the seat at row 2, column 3 to "Taken".
C Sharp (C#)
Hint

Use the syntax seats[row, column] = "Taken"; to mark seats.

3
Loop through the seats to prepare output
Use nested for loops with variables row and col to go through each seat in seats. Inside the inner loop, build a string called rowSeats that joins seat statuses separated by spaces for each row.
C Sharp (C#)
Hint

Use seats.GetLength(0) for rows and seats.GetLength(1) for columns. Add each seat to rowSeats with a space.

4
Print the seating arrangement
Run the program to print the seating arrangement showing which seats are "Free" and which are "Taken".
C Sharp (C#)
Hint

Run the program and check the console output matches the seating arrangement.

Practice

(1/5)
1. What is a multi-dimensional array in C#?
easy
A. An array that can only hold one value
B. An array that stores only strings
C. An array with more than one dimension, like rows and columns
D. A list of unrelated variables

Solution

  1. Step 1: Understand array dimensions

    A multi-dimensional array stores data in multiple dimensions, such as rows and columns, unlike a simple one-dimensional array.

  2. Step 2: Recognize the definition

    An array with more than one dimension, like rows and columns correctly describes a multi-dimensional array as having more than one dimension, like a table with rows and columns.

  3. Final Answer:

    An array with more than one dimension, like rows and columns -> Option C

  4. Quick Check:

    Multi-dimensional array = rows and columns [OK]
Hint: Think of a table with rows and columns [OK]
Common Mistakes:
  • Confusing multi-dimensional arrays with simple lists
  • Thinking arrays can only hold one type of data
  • Believing multi-dimensional arrays are unrelated variables
2. Which of the following is the correct way to declare a 2x3 multi-dimensional array of integers in C#?
easy
A. int[,] arr = new int[2,3];
B. int[][] arr = new int[2][3];
C. int arr[2,3];
D. int arr = new int[2,3];

Solution

  1. Step 1: Recall C# multi-dimensional array syntax

    In C#, a 2D array is declared with commas inside square brackets: int[,] arr = new int[rows, columns];

  2. Step 2: Check each option

    int[,] arr = new int[2,3]; uses correct syntax. int[][] arr = new int[2][3]; is jagged array syntax, not multi-dimensional. Options A and C are invalid syntax.

  3. Final Answer:

    int[,] arr = new int[2,3]; -> Option A

  4. Quick Check:

    Use comma inside brackets for multi-dimensional arrays [OK]
Hint: Use comma inside brackets for multi-dimensional arrays [OK]
Common Mistakes:
  • Using jagged array syntax instead of multi-dimensional
  • Missing 'new' keyword or wrong brackets
  • Confusing array declaration with other languages
3. What will be the output of the following C# code?
int[,] matrix = { {1, 2, 3}, {4, 5, 6} };
Console.WriteLine(matrix[1, 2]);
medium
A. 3
B. 5
C. Runtime error
D. 6

Solution

  1. Step 1: Understand array indexing

    matrix[1, 2] means row 1, column 2. Rows and columns start at 0.

  2. Step 2: Locate the value at matrix[1, 2]

    Row 1 is {4, 5, 6}, column 2 is the third element, which is 6.

  3. Final Answer:

    6 -> Option D

  4. Quick Check:

    matrix[1,2] = 6 [OK]
Hint: Remember indexing starts at zero for rows and columns [OK]
Common Mistakes:
  • Confusing row and column indexes
  • Starting count from 1 instead of 0
  • Expecting the value 3 or 5 instead of 6
4. Identify the error in this C# code snippet:
int[,] grid = new int[3, 3];
grid[3, 0] = 10;
medium
A. Index out of range error at grid[3, 0]
B. Syntax error in array declaration
C. Missing initialization of array
D. No error, code runs fine

Solution

  1. Step 1: Check array size and valid indexes

    The array grid has size 3x3, so valid row indexes are 0, 1, 2.

  2. Step 2: Analyze the assignment grid[3, 0]

    Index 3 for row is out of range, causing an IndexOutOfRangeException at runtime.

  3. Final Answer:

    Index out of range error at grid[3, 0] -> Option A

  4. Quick Check:

    Index 3 invalid for size 3 array [OK]
Hint: Indexes start at 0, max index is size-1 [OK]
Common Mistakes:
  • Using index equal to array size
  • Confusing syntax error with runtime error
  • Assuming arrays auto-expand on invalid index
5. Given a 3x3 multi-dimensional array int[,] board representing a tic-tac-toe game, which code snippet correctly counts how many cells contain the value 1?
int count = 0;
// Which loop is correct?
A) for (int i = 0; i < 3; i++)
   for (int j = 0; j < 3; j++)
       if (board[i, j] == 1) count++;

B) for (int i = 1; i <= 3; i++)
   for (int j = 1; j <= 3; j++)
       if (board[i, j] == 1) count++;

C) for (int i = 0; i < 3; i++)
   for (int j = 0; j < 2; j++)
       if (board[i, j] == 1) count++;

D) for (int i = 0; i < 3; i++)
   for (int j = 0; j < 3; j++)
       if (board[j, i] == 1) count++;
hard
A. rorre egnar fo tuo xedni sesuaC
B. Causes index out of range error
C. Misses last column in counting
D. Counts transposed cells, not original positions

Solution

  1. Step 1: Understand array indexing and loop ranges

    Indexes start at 0 and go up to size-1, so loops must run from 0 to less than 3.

  2. Step 2: Analyze each option's loops

    Causes index out of range error correctly counts all cells with value 1 loops correctly over all rows and columns. Causes index out of range error causes index out of range error uses 1 to 3, causing out of range. Misses last column in counting misses last column by looping j to 2. Counts transposed cells, not original positions swaps indexes, counting transposed cells.

  3. Final Answer:

    Causes index out of range error -> Option B

  4. Quick Check:

    Loop from 0 to less than size for rows and columns [OK]
Hint: Loop indexes from 0 to size-1 for all dimensions [OK]
Common Mistakes:
  • Starting loops at 1 instead of 0
  • Using wrong loop limits causing missed elements
  • Swapping row and column indexes accidentally
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