4.1) Multidimensional Arrays in C

What are Multidimensional Arrays?

Multidimensional arrays in C allow you to store data in a table-like structure with multiple rows and columns. These arrays are essentially arrays of arrays, allowing you to represent more complex data structures, such as matrices.

It’s like having a bunch of boxes arranged in rows and columns, and you can put numbers or other things inside those boxes.

Declaring and Using a 2D Array:

Multidimensional arrays are declared using the syntax:

data_type array_name[row_size][column_size];

You can initialize multidimensional arrays during declaration using nested curly braces {}.

Let’s say you want to make a 2D array to store students’ scores in different subjects. Here’s how you can do it:

#include <stdio.h>

int main() {
    // Declaring and initializing a 2D array (2 rows, 3 columns)
    int scores[2][3] = {
        {90, 85, 78},
        {67, 92, 88}
    };

    // Accessing elements using row and column indices
    printf("Score at row 1, column 2: %d\n", scores[0][1]);  // 85

    return 0;
}

Explanation:

• We declare an array called scores with 2 rows and 3 columns to store students’ scores.
• We put numbers in the array to represent the scores for each student and each subject.
• To access a score, we use scores[row_index][column_index]. For example, scores[0][1] is the score in the first row (student 1) and second column (subject 2), which is 85.

Using Loops to Work with 2D Arrays:

Using loops can help us easily go through all the elements in a 2D array.

#include <stdio.h>

int main() {
    int scores[2][3] = {
        {90, 85, 78},
        {67, 92, 88}
    };

    // Printing all scores using nested loops
    for (int i = 0; i < 2; i++) {
        for (int j = 0; j < 3; j++) {
            printf("Score at row %d, column %d: %d\n", i, j, scores[i][j]);
        }
    }

    return 0;
}

Explanation:

• We use two nested loops, one for rows and one for columns, to go through each score in the array.
• The i loop variable represents the row, and the j loop variable represents the column.
• We use scores[i][j] to access the score at the current row and column.

Creating a 3D Array:

Think of a 3D array as a bunch of 2D arrays stacked on top of each other. You can use it to store more complex information, like in a game where you might have a grid of tiles for a 2D map, and you want multiple maps for different levels.

#include <stdio.h>

int main() {
    // Declaring and initializing a 3D array (2 maps, 3 rows, 4 columns)
    int gameMaps[2][3][4] = {
        {
            {1, 2, 3, 4},
            {5, 6, 7, 8},
            {9, 10, 11, 12}
        },
        {
            {13, 14, 15, 16},
            {17, 18, 19, 20},
            {21, 22, 23, 24}
        }
    };

    // Accessing elements using indices for each dimension
    printf("Element at map 1, row 2, column 3: %d\n", gameMaps[0][1][2]);  // 7

    return 0;
}

Explanation:

• We declare a 3D array named gameMaps with 2 maps, 3 rows, and 4 columns.
• Each map is like a 2D array. We can access elements using three indices: gameMaps[map_index][row_index][column_index].

Remember:

• Multidimensional arrays are like tables with rows and columns.
• To access an element, use multiple indices like array[row_index][column_index].
• Loops are great for working with these arrays, especially nested loops for 2D arrays.
• 3D arrays are like having multiple 2D arrays stacked together.

Accessing Elements of a 3×3 Array Using Nested Loops

#include <stdio.h>

int main() {
    // Declaring and initializing a 3x3 array
    int grid[3][3] = {
        {1, 2, 3},
        {4, 5, 6},
        {7, 8, 9}
    };

    // Accessing elements using nested loops
    for (int i = 0; i < 3; i++) {
        for (int j = 0; j < 3; j++) {
            printf("%d ", grid[i][j]);
        }
        printf("\n");
    }

    return 0;
}

Real-world example of a 2D array in C

We’ll create a program to manage a simple student gradebook using a 2D array.

The program will allow us to input and display student names and their corresponding grades for different subjects.

#include <stdio.h>

#define NUM_STUDENTS 3
#define NUM_SUBJECTS 5

int main() {
    // Declare a 2D array to store student grades
    int grades[NUM_STUDENTS][NUM_SUBJECTS];

    // Input student names and grades
    char studentNames[NUM_STUDENTS][50];
    for (int i = 0; i < NUM_STUDENTS; i++) {
        printf("Enter name of student %d: ", i + 1);
        scanf("%s", studentNames[i]);

        printf("Enter grades for student %d (5 subjects):\n", i + 1);
        for (int j = 0; j < NUM_SUBJECTS; j++) {
            printf("Subject %d: ", j + 1);
            scanf("%d", &grades[i][j]);
        }
    }

    // Display student names and grades
    printf("\nStudent Gradebook:\n");
    for (int i = 0; i < NUM_STUDENTS; i++) {
        printf("Name: %s\n", studentNames[i]);
        printf("Grades: ");
        for (int j = 0; j < NUM_SUBJECTS; j++) {
            printf("%d ", grades[i][j]);
        }
        printf("\n\n");
    }

    return 0;
}

Explanation:

1. We define NUM_STUDENTS and NUM_SUBJECTS constants to specify the size of the 2D array.
2. We declare a 2D array grades to store student grades. It has dimensions NUM_STUDENTS by NUM_SUBJECTS.
3. We declare another 2D array studentNames to store student names. Each row corresponds to a student.
4. We use nested loops to input student names and grades. The outer loop iterates over students, and the inner loop iterates over subjects.
5. We use scanf to input student names and grades from the user.
6. After input, we use another set of nested loops to display the student names and grades. We print each student’s name and their corresponding grades for each subject.

Example Interaction:

Enter name of student 1: Alice
Enter grades for student 1 (5 subjects):
Subject 1: 90
Subject 2: 85
Subject 3: 78
Subject 4: 92
Subject 5: 88
Enter name of student 2: Bob
Enter grades for student 2 (5 subjects):
Subject 1: 75
Subject 2: 82
Subject 3: 95
Subject 4: 70
Subject 5: 68
Enter name of student 3: Carol
Enter grades for student 3 (5 subjects):
Subject 1: 88
Subject 2: 92
Subject 3: 85
Subject 4: 78
Subject 5: 90

Student Gradebook:
Name: Alice
Grades: 90 85 78 92 88 

Name: Bob
Grades: 75 82 95 70 68 

Name: Carol
Grades: 88 92 85 78 90 

In this example, we’ve used a 2D array to store student grades and names. This demonstrates how 2D arrays can be used to represent and manage structured data in real-world scenarios, such as a gradebook management system.