Question

1. declare a struct named matrix and typedef the struct to type name Matrix. A mathematical matrix is a two-dimensional, rectangular data structure. The matrix struct should have three fields (in this order): an unsigned variable named "rows", an unsigned variable named "columns", and a pointer to a pointer to double (i.e. double**) named "data". (Code #including matrix.h should be able to declare Matrix variables.)
2. In matrix.c, implement the create_matrix function. The Matrix should be filled with 0.0 values. data[i] should be a pointer to the ith row. data[i][j] should be the value in the ith row and jth column.
3. In matrix.c, implement the print_matrix function. The function should print the matrix's data, one row per line with a single space between elements and a newline at the end of each row. Each data value should be printed with 6 digits to the right of the decimal point.
4. In matrix.c, implement the free_matrix function. The function should free all the matrix's data that was dynamically allocated in the create_matrix function.

Answer 1

Solution

/*** matrix.h ***/

#ifndef MATRIX_H
#define MATRIX_H

//Matrix structure definition
typedef struct
{
unsigned rows;
unsigned columns;
double **data;
}Matrix;

//function prototypes
Matrix create_matrix(unsigned r, unsigned c);
void print_matrix(Matrix mat);
void free_matrix(Matrix mat);

#endif // MATRIX_H

/*** matrix.c ***/

#include <stdio.h>
#include <stdlib.h>
#include"matrix.h"

//function to create Matrix
Matrix create_matrix(unsigned rows, unsigned columns)
{
Matrix mat;
mat.columns = columns;
mat.rows = rows;

mat.data =(double**)malloc(rows * sizeof(double*));
double *q =(double*)malloc(rows * columns * sizeof(double));

for(unsigned i=0; i<rows; i++)
{
mat.data[i] = q;
q += columns;
}

for(unsigned i=0; i<rows; i++)
for(unsigned j=0; j<columns; j++)
mat.data[i][j] = 0.0;

return mat;
}

//function to print the Matrix
void print_matrix(Matrix mat)
{
for(unsigned i=0; i<mat.rows; i++){
for(unsigned j=0; j<mat.columns; j++)
printf("%0.6f ", mat.data[i][j]);
printf("\n");
}
}

//function to free the Matrix
void free_matrix(Matrix mat)
{
for(unsigned i=0; i<mat.rows; i++)
{
free(mat.data[i]);
}
free(mat.data);
}

/*** main.cpp */

#include <stdio.h>
#include <stdlib.h>
#include"matrix.h"

//main function
int main()
{
int rows = 3;
int columns = 3;

Matrix mat = create_matrix(rows, columns);
print_matrix(mat);
free_matrix(mat);

return 0;
}

Output:

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