Dynamic allocation of multi dimensional array

pointer · #1 12-May-2005, 10:42

Hi everyone, could you tell me how to assign values to a dynamically created multi dimensional array?

I tried this code. I am getting error : Invalid direction

CPP / C++ / C Code:

#include<stdio.h>
#include<conio.h>
main()
{
	int *a;
	int i,j,k;
	int l,m,n;
	//clrscr();
	printf("Enter i,j,k value to create multidimensional array:");
	scanf("%d  %d  %d",&i,&j,&k);
	printf("I=%d  J=%d  K=%d",i,j,k);
	a=(int *)malloc(i*j*k*sizeof(int));
	for(l=0;l<i;l++)
	{
		for(m=0;m<j;m++)
		{
			for(n=0;n<k;n++)
			{
				printf("Enter array elements:");
				a[n][m][k])=getche();
			}
		}
	}
	for(l=0;l<i;l++)
	{
		printf("\n");
		for(m=0;m<j;m++)
		{
			for(n=0;n<k;n++)
			{
				printf("%d",a[n,m,k]);  /* Error at this line: Invalid indirection */

			}
		}
	}

	getch();


}

Anyone can help me to assign values?

maprich · #2 12-May-2005, 11:00

CPP / C++ / C Code:

				printf("Enter array elements:");
				a[n][m][k])=getche();

Shouldn't that be

CPP / C++ / C Code:

				printf("Enter array elements:");
				a[n][m][l])=getche();

also...

CPP / C++ / C Code:

printf("%d",a[n,m,k]);

should be

CPP / C++ / C Code:

printf("%i", a[n][m][l] );

pointer · #3 12-May-2005, 13:42

I tried that also, I am getting same error at the line: scanf("%d",a[n][m][k]);

maprich · #4 12-May-2005, 13:51

Please read my previous posting more carefully. k is not l. l is not k.

pointer · #5 13-May-2005, 11:37

Quote:

Originally Posted by maprich

Please read my previous posting more carefully. k is not l. l is not k.

Some how I got answer but some mistakes is there. I will post my code. Can you tell me what is wrong in my code??

CPP / C++ / C Code:

#include<stdio.h>
#include<conio.h>
main()
{
	int *a;
	int i,j,k;
	int l,m,n;


	clrscr();

	printf("Enter i,j,k value to create multidimensional array:");
	scanf("%d  %d  %d",&i,&j,&k);

	printf("I=%d  J=%d  K=%d\n",i,j,k);

	a=(int *)malloc(i*j*k*sizeof(int));

	if(a==NULL)
		printf("Error:array not initialised\n");
	else
	{
	   for(l=0;l<i;l++)
	   {
	      printf("\n");
		for(m=0;m<j;m++)
		{
		   for(n=0;n<k;n++)
		   {
			printf("Enter Elements:");
			scanf("%d",(((a+l)+m)+n));
			printf("a[%d][%d][%d]=%d",l,m,n,*(((a+l)+m)+n));

		   }

		}
	}   }
	for(l=0;l<i;l++)
	{
		printf("\n");
		for(m=0;m<j;m++)
		{
			printf("\n");
			for(n=0;n<k;n++)
			{
				printf("a[%d][%d][%d]=%2d  ",l,m,n,*(((a+l)+m)+n));

			}
		}
	}

	getch();


}

maprich · #6 13-May-2005, 12:33

Yes first of all sorry. My previous posting was quite wrong; I did a mistake because c++ and c got mixed up in my mind. It is true that in c you cannot refer to multidimensional array with a[n][m][l].. but in c++ you can because the compiler has more information about the dimensions of the table. .. ok .. but back to the problem.

i think you should write like:

Code:

a[ n*j*i+m*i+l ]

Whenever you need to refer to a coordinate aka a[n][m][l]
this is because l runs from 0 to (i-1), m is the 2.dimension so with every unit increase in m the pointer must jump i and finally n is for the 3.dimension..etc..
so write:

CPP / C++ / C Code:

scanf("%d", &a[n*j*i+m*i+l] )

and

CPP / C++ / C Code:

printf("a[%d][%d][%d]=%d",l,m,n, a[n*j*i+m*i+l] );

hopefully works

Dave Sinkula · #7 13-May-2005, 14:26

http://www.eskimo.com/~scs/C-faq/q6.16.html
http://www.parashift.com/c++-faq-lit...html#faq-16.16

WaltP · #8 14-May-2005, 00:50

Quote:

Originally Posted by pointer

Can you tell me what is wrong...

Yeah, after numerous requests, you refuse to use code tags. Read the sticky and start posting messages that don't have to be cleaned up by the admins...

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