Memory allocation for pointer to array and array of pointer - c

Question

Below is the part of code I am stuck on. I want to dynamically allocate memory for
Pointer to array
Array of pointers
I am getting several error messages like invalid conversion from int * to int and so on.
Pointer to array
int (*array)[nrows][ncolumns];
array = (int*)malloc(nrows * ncolumns * sizeof(int));
printf("\n Enter the elements:\n");
for(i=0; i<nrows; i++)
{
for(j=0; j<ncolumns; j++)
{
scanf("%d", array[i][j]);
}
}
printf("Entered array is :\n\n");
for(i = 0;i<nrows; i++)
{
for(j = 0; j<ncolumns; j++)
{
if(j== ncolumns-1)
{
printf("%d \n", *array[i][j]);
}
else
{
printf("%d", *array[i][j]);
}
Array of pointers
int *array[nrows][ncolumns];
array[nrows][ncolumns] = (int*)malloc(nrows * ncolumns * sizeof(int));
printf("Enter elements:\n");
for(i = 0; i<nrows; i++)
{
for(j = 0; j<ncolumns;j++)
{
scanf("%d",&array[i][j]);
}
}
printf("Entered array is: \n");
for(i = 0; i<nrows; i++)
{
for(j = 0; j<ncolumns;j++)
{
if(j == ncolumns-1)
{
printf("%d \n",array[i][j]);
}
else
{
printf("%d \t",array[i][j]);
}
}
}

Answer 1

1> pointer to array
#include <stdio.h>
#include <stdlib.h>
int main(void){
int nrows = 3;
int ncolumns = 4;
int i, j;
int (*array)[nrows][ncolumns];//do you want <<int (*array)[ncolumns]>> ?
//like as int src[nrows][ncolumns]; array = &src;
array = malloc(nrows * ncolumns * sizeof(int));//(int*) : type mismatch
printf("\nEnter the elements:\n");
for(i = 0; i<nrows; i++){
for(j = 0; j<ncolumns; j++){
scanf("%d", &(*array)[i][j]);
}
}
printf("Entered array is :\n\n");
for(i = 0; i<nrows; i++){
for(j = 0; j<ncolumns; j++){
if(j != 0)
putchar(' ');
printf("%d", (*array)[i][j]);//need ( )
}
putchar('\n');
}
free(array);
return 0;
}
2> Array of pointers
#include <stdio.h>
#include <stdlib.h>
int main(void){
int nrows = 3;
int ncolumns = 4;
int i, j;
int *array[nrows][ncolumns];
int *src = (int*)malloc(nrows * ncolumns * sizeof(int));//no need (int*)
printf("Enter elements:\n");
for(i = 0; i<nrows; i++){
for(j = 0; j<ncolumns;j++){
array[i][j] = &src[ i * ncolumns + j];//pointer pointed to entity (src[ i * ncolumns + j])
scanf("%d", array[i][j]);//type of array[i][j] is int *
}
}
printf("Entered array is: \n");
for(i = 0; i<nrows; i++){
for(j = 0; j<ncolumns; j++){
if(j != 0)
putchar(' ');
printf("%d", *array[i][j]);//need * for dereference
}
putchar('\n');
}
free(src);
return 0;
}
3> option
#include <stdio.h>
#include <stdlib.h>
int main(void){
int nrows = 3;
int ncolumns = 4;
int i, j;
int (*array)[ncolumns];
array = (int (*)[ncolumns])malloc(nrows * sizeof(*array));//sizeof(*array) : sizeof(int[ncolumns])
printf("\nEnter the elements:\n");
for(i = 0; i<nrows; i++){
for(j = 0; j<ncolumns; j++){
scanf("%d", &array[i][j]);
}
}
printf("Entered array is :\n\n");
for(i = 0; i<nrows; i++){
for(j = 0; j<ncolumns; j++){
if(j != 0)
putchar(' ');
printf("%d", array[i][j]);
}
putchar('\n');
}
free(array);
return 0;
}