Passing Two-Dimensional Arrays to Functions

PASSING TWO-DIMENSIONAL ARRAYS TO FUNCTIONS

There are three ways of passing two-dimensional arrays to functions. First, we can pass individual elements of the array. This is exactly same as passing elements of a one-dimensional array. Second, we can pass a single row of the two-dimensional array. This is equivalent to passing the entire one-dimensional array to a function. This has already been discussed in the previous section.. Third, we can pass the entire two-dimensional array to the function. Refer Figure 5.30 which shows the three ways of using two-dimensional arrays for inter-function communication.

Passing a Row

A row of a two-dimensional array can be passed by indexing the array name with the row number. When we send a single row of a two-dimensional array, then the called function receives a one-dimensional array. Figure 5.31 illustrates how a single row of a two-dimensional array is passed to the called function.

Passing an Entire 2D Array

To pass a two-dimensional array to a function, we use the array name as the actual parameter. However, the parameter in the called function must indicate that the array has two dimensions.

31. Write a menu-driven program to read and display an m × n matrix. Also find the sum, transpose, and product of two m x n matrices.

#include <stdio.h>

#include <conio.h>

Programming Tip: A compiler error will be generated if you omit the array size in the parameter declaration for any array dimension other than the first.

void read_matrix (int mat [2] [2], int, int);

void sum matrix (int mat1 [2] [2], int mat2 [2] [2], int, int);

void mul matrix (int mat1 [2] [2], int mat2 [2] [2], int, int);

void transpose_matrix (int mat2 [2] [2], int, int);

void display_matrix (int mat [2] [2], int r, int c);

int main()

{

int mat1 [2] [2], mat2 [2] [2];

clrscr();

do

{

printf("\n ******* MAIN MENU ********") ;

printf("\n 1. Read the two matrices");

printf("\n 2. Add the matrices");

printf("\n 3. Multiply the matrices");

printf("\n 4. Transpose the matrix");

printf("\n 5. EXIT");

printf("\n\n Enter your option: ");

scanf("%d", &option);

switch (option)

{

case 1:

printf("\n Enter the number of rows and columns of the matrix: ");

scanf("%d %d", &row, &col);

printf("\n Enter the first matrix: ");

read_matrix (matl, row, col);

printf("\n Enter the second matrix: ");

read matrix (mat2, row, col);

break;

case 2:

sum matrix (mat1, mat2, row, col);

break;

case 3:

if (col = = row)

mul_matrix (mat1, mat2, row, col);

else

printf("\n To multiply two matrices, number of columns in the first matrix must be equal to number of rows in the second matrix");

break;

case 4:

transpose_matrix (mat1, row, col);

break;

}

} while (option != 5);

getch();

return 0;

}

void read matrix (int mat [2] [2], int r, int c)

{

int i, j;

for (i = 0; i < r;i++)

{ printf("\n");

for(j = 0; j < C;j++)

{

printf("\t mat [%d] [%d] = ",i,j);

scanf("%d", &mat [i] [j]);

}

}

}

void sum matrix (int mat1 [2] [2], int mat2 [2] [2], int r, int c)

{

int i, j, sum [2] [2];

for (i=0;i<r;i++)

{

for(j=0;j<c;j++)

sum [i][j] = mat1 [i][j] + mat2 [i][j];

}

display_matrix (sum, r, c);

}

void mul_matrix (int mat1 [2] [2], int mat2 [2] [2], int r, int c)

{

int i, j, k, prod [2] [2];

for (i=0; i<r; i++)

{

for(j=0;j<c;j++)

{

prod[i][j] = 0;

for (k=0;k<c;k++)

prod [i][j] += mat1 [i] [k] * mat2 [k] [j];

}

}

display_matrix (prod, r, c);

}

void transpose_matrix (int mat [2] [2], int r,int c)

{

int i, j, tp_mat [2] [2];

for (i=0;i<r;i++)

{

for(j=0;j<c;j++)

tp_mat [j] [i] = mat [i][j];

}

display_matrix (tp_mat, r, c);

}

void display_matrix (int mat [2] [2], int r,int c)

{

int i, j;

for (i=0;i<r;i++)

{

printf("\n");

for(j=0;j<c;j++)

printf("\t mat [%d] [%d] = %d", i, j, mat [i] [j]);

}

}

Output

******* MAIN MENU ********

1. Read the two matrices

2. Add the matrices

3. Multiply the matrices

4. Transpose the matrix

5. EXIT

Enter your option: 1

Enter the number of rows and columns of the matrix: 2 2

Enter the first matrix:

mat [0] [0] = 1 mat [0] [1] = 2

mat [1] [0] = 3 mat [1] [1] = 4

Enter the second matrix :

mat [0] [0] = 2 mat [0] [1] = 3

mat [1] [0] = 4 mat [1] [1] = 5

******* MAIN MENU ********

1. Read the two matrices

2. Add the matrices

3. Multiply the matrices

4. Transpose the matrix

5. EXIT

Enter your option: 2

mat [0] [0] = 3  mat [0] [1] = 5

mat [1] [0] = 7  mat [1] [1] = 9

``````````

32. Write a program to fill a square matrix with value zero on the diagonals, 1 on the upper right triangle, and -1 on the lower left triangle.

#include <stdio.h>

#include <conio.h>

void read_matrix (int mat [5] [5], int);

void display_matrix (int mat [5] [5], int);

int main()

{

int row;

int mat [5] [5];

clrscr();

printf("\n Enter the number of rows and columns of the matrix ");

scanf("%d", &row);

read matrix (mat, row);

display_matrix (mat, row);

getch();

return 0;

}

void read_matrix (int mat [5] [5], int r)

{

int i, j;

for (i = 0; i < r;i++)

{

for (j = 0; j < r;j++)

{

if (i==j)

mat [i] [j] = 0;

else if (i>j)

mat [i][j] = -1;

else

mat [i][j] = 1;

}

}

}

void display_matrix (int mat [5] [5], int r)

{

int i, j;

for (i=0; i<r; i++)

{

printf("\n");

for(j=0;j<r;j++)

printf("\t %d", mat [i] [j]);

}

 }

Output

Enter the number of rows and columns of the matrix: 2

0   1

-1  0