Help printing a multi array

**cjohnman** · 05-05-2008

I am having difficulty trying to use a pointer to print contents of an array. With the simple array below how could I use a pointer to print out the contents? I know I can use multi[x][x] but I would like to use a pointer instead. Is this where I need to learn casting? I am just printing different variables so I can learn how this works. Any help using a pointer of some type to print the contents of my array is greatly appreciated. One row at a time would be nice.

Code:

   int multi[3][4] = {{1,2,3,4},{5,6,7,8},{9,10,11,12}};
    
   int (*ptr)[4], count;
   
   ptr = multi;
  

   printf("&#37;d\n", ptr);
   printf("%d\n", *ptr);
   printf("%d\n", multi);
   printf("%d\n", multi[0]);
   printf("%d\n", multi[0][0]);

    ++ptr;
 
   printf("%d\n", ptr);
   printf("%d\n", *ptr);
   printf("%d\n", multi);
   printf("%d\n", multi[0]);
   printf("%d\n", multi[0][0]);
   printf("%u\n", sizeof(multi[0]));
   printf("%d\n", sizeof(multi[0][0]));

**Dino** · 05-05-2008

Here's one way.

Code:

#include <stdio.h>

#define ROWS 3 
#define COLS 4 
 
int main() { 

	int multi[ROWS][COLS] = {{1,2,3,4},{5,6,7,8},{9,10,11,12}};
    
	int * ptr1 ; 
	
	ptr1 = &multi[0][0];
	int i , j ; 
	
	for (i = 0  ; i < ROWS  ; i++ ) { 
		for (j = 0  ; j < COLS  ; j++ ) { 
			printf("The value @ [&#37;d][%d] is %d\n", i,j,*ptr1 ) ; 
			ptr1++ ; 
		}
	}
	return 0 ; 
}

**cjohnman** · 05-05-2008

I am trying to learn how to use pointer in this fashion...int (*ptr)[4]. Is that not neccessary? The book I am reading uses the pointer that way but then does this... p= (int *)ptr; in a function and when I do it I get a compile error... Operation between types "int(*)[4]" and "int*" is not allowed. Could you give me an example doing it this other way? Thanks always for your help.

**Dino** · 05-05-2008

No I can't - haven't done that yet.

**Salem** · 05-05-2008

> I know I can use multi[x][x]
Try ptr[x][x] as well

(*ptr)[x]
would print the first row, x = 0 to 3

*ptr being the equivalent of ptr[0]

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Help printing a multi array

That makes sense but....

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