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Multi-dimensional Arrays in C: A Comprehensive Guide

Explore the concept of multi-dimensional arrays in C, which allow you to efficiently store and manipulate data in a structured format.

Multi-dimensional Arrays in C

An array with one size value in square brackets is a one-dimensional array. Each element is identified by its index. In C, you can use more indices to create two, three, or more dimensions.

Declaration

Multi-dimensional arrays are declared with multiple sizes:

Syntax

type name[size1][size2]...[sizeN];

Example of a three-dimensional array:

Syntax

int threedim[2][3][4];

Two-dimensional Array in C

A two-dimensional array is an array of one-dimensional arrays, like a table with rows and columns. Each element is identified by its row and column indices, both starting at 0.

Declaration and Initialization

Declare and initialize a two-dimensional array:

Syntax

int arr[3][4] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12};

Each row can be separately enclosed in curly brackets for readability:

Syntax

int arr[3][4] = {
   {1, 2, 3, 4}, 
   {5, 6, 7, 8}, 
   {9, 10, 11, 12}
};

Example: Printing Elements

Print row and column indices of a 2D array:

Code

#include <stdio.h>
int main() {
   int a[3][2] = { {1, 2}, {3, 4}, {5, 6} };
   int i, j;

   for (i = 0; i < 3; i++) {
      for (j = 0; j < 2; j++) {
         printf("a[%d][%d] = %d\n", i, j, a[i][j]);
      }
   }

   return 0;
}
Output

a[0][0] = 1
a[0][1] = 2
a[1][0] = 3
a[1][1] = 4
a[2][0] = 5
a[2][1] = 6

Example: Printing as Matrix

Print a 2D array as a matrix:

Code

#include <stdio.h>

int main() {
   int arr[3][4] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12};
   int i, j;

   for (i = 0; i < 3; i++) {
      for (j = 0; j < 4; j++) {
         printf("%4d", arr[i][j]);
      }
      printf("\n");
   }

   return 0;
}
Output

   1   2   3   4
   5   6   7   8
   9  10  11  12

Three-dimensional Array in C

A three-dimensional array is an array of two-dimensional arrays, needing three indices: depth, row, and column.

Example: Printing 3D Array Elements

Print elements of a 3D array:

Code

#include <stdio.h>

int main() {
   int arr[2][2][2] = {
      {{1, 2}, {3, 4}},
      {{5, 6}, {7, 8}}
   };
   int i, j, k;

   printf("Printing 3D Array Elements\n");

   for (i = 0; i < 2; i++) {
      for(j = 0; j < 2; j++) {
        for (k = 0; k < 2; k++) {
           printf("%4d", arr[i][j][k]);
        }
        printf("\n");
     }
     printf("\n");

     }

return 0;
}
Output

Printing 3D Array Elements
   1   2
   3   4
5 6
7 8

Row-wise Sum of Elements

Calculate and display the sum of each row in a 2D array:

Code

#include <stdio.h>
int main() {
int arr[3][4] = { {1, 2, 3, 4}, {5, 6, 7, 8}, {9, 10, 11, 12} };
int i, j, sum;

for (i = 0; i < 3; i++) {
sum = 0;
for (j = 0; j < 4; j++) {
sum += arr[i][j];
}
printf("Sum of row %d: %d\n", i, sum);
}

return 0;
}
Output

Sum of row 0: 10
Sum of row 1: 26
Sum of row 2: 42

Matrix Multiplication

Matrix multiplication involves multiplying rows of the first matrix by columns of the second matrix. The resulting matrix has the number of rows of the first matrix and the number of columns of the second matrix.

Example: Multiplying Two Matrices

Code

#include <stdio.h>
int main() {
int mat1[2][3] = { {1, 2, 3}, {4, 5, 6} };
int mat2[3][2] = { {7, 8}, {9, 10}, {11, 12} };
int mat3[2][2] = {0};
int i, j, k;

for (i = 0; i < 2; i++) {
for (j = 0; j < 2; j++) {
for (k = 0; k < 3; k++) {
mat3[i][j] += mat1[i][k] * mat2[k][j];
}
}
}

printf("Matrix 1:\n");
for (i = 0; i < 2; i++) {
for (j = 0; j < 3; j++) {
printf("%d ", mat1[i][j]);
}
printf("\n");
}

printf("Matrix 2:\n");
for (i = 0; i < 3; i++) {
for (j = 0; j < 2; j++) {
printf("%d ", mat2[i][j]);
}
printf("\n");
}

printf("Result of Multiplication:\n");
for (i = 0; i < 2; i++) {
for (j = 0; j < 2; j++) {
printf("%d ", mat3[i][j]);
}
printf("\n");
}

return 0;
}
Output

Matrix 1:
1 2 3
4 5 6
Matrix 2:
7 8
9 10
11 12
Result of Multiplication:
58 64
139 154