Print Matrix Trying to have a 2D array parameter in a function in C isn\'t as si

Question

Print Matrix Trying to have a 2D array parameter in a function in C isn't as simple as in Java. Like with single dimensional arrays, it's common to actually make the parameter a pointer to a pointer type rather than an actual array type. Create a function to print a 2D array of characters. Write a program that asks the user for a height and width and dynamically allocates a 2D array of those dimensions. Fill the array with dots and then randomly put asterisks in some elements. For the number of asterisks, it should be 10% of the width times the height cast to an int (for example, 10 * 10 * 0.1 = 10). Then, use the print function on the array. Here's the function header to get you started:

void print_matrix(char ** matrix, int height, int width)

Sample Run:

Enter Height: 10

Enter Width: 10

Asterisk Count: 10

array (0x7f939d600000):

. . . * . . . . . .

. . . . . . . . . .

. . . . . . . . . .

. . . * . . . . . .

. . . * . . . * . .

. . . . . . . . . .

. * . . . * . . . .

. . . . . . . * . *

. . * . . . . * . .

. . . . . . . . . .

Explanation / Answer

Here is the program which takes array as a double pointer.

#include<stdio.h>

#include<stdlib.h>

long random_at_most(long max) {

unsigned long

// max <= RAND_MAX < ULONG_MAX, so this is okay.

num_bins = (unsigned long) max + 1,

num_rand = (unsigned long) RAND_MAX + 1,

bin_size = num_rand / num_bins,

defect = num_rand % num_bins;

long x;

do {

x = rand();

}

// This is carefully written not to overflow

while (num_rand - defect <= (unsigned long)x);

// Truncated division is intentional

return x/bin_size;

}

void print_matrix(char **matrix, int r, int c){

int i,j,x,rand1,rand2,count;

// adding dots to the array

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

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

matrix[i][j] = '.'; // OR *(*(arr+i)+j) = ++count

//calculate the no of stars to be printed

x = (int)(r*c*0.1);

//adding stars to the array

count=0;

while(count<x){

//srand(time(NULL));

rand1 =(int) rand()%10+1;

//srand(time(NULL));

rand1 = (int)rand()%10+1;

//if(rand1 < r && rand2 < c){

matrix[rand1][rand2]='*';

count++;

//}

}

//printing array

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

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

printf("%c ", matrix[i][j]);

}

printf(" ");

}

}

int main() {

int height,width,i;

char **matrix;

clrscr();

//taking height from user

printf("Enter Height ");

scanf("%d",&height);

//taking width from user

printf("Enter Width ");

scanf("%d",&width);

//allocating memory for 2d array

matrix = (char **)malloc(height * sizeof(char *));

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

matrix[i] = (char *)malloc(width * sizeof(char));

//calling function to print matrix

print_matrix(matrix, height, width);

getch();

return 0;

}

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