Programming

Question

#include <stdio.h>

int main()
{
    int arr[5], brr[5][5], crr[5][5][5];
    int i,j,k;
    for(i=0;i<5;i++)
    arr[i] = i;
    
    for(i=0;i<5;i++)
    {
        for(j=0;j<5;j++)
        {
            brr[i][j] = i+ j;
        }
    }
    
    for(i=0;i<5;i++)
    {
        for(j=0;j<5;j++)
        {
            for(k=0;k<5;k++)
            {
                crr[i][j][k] = i+j+k;
            }
        }
    }
    int *ptr1, **ptr2, ***ptr3;
    
    ptr1 = crr;
    printf("%d", *(ptr1+3));
    return 0;
}

Why it is printing the value inside the array?

As per my knowledge, crr means BA of 0th 2D array as crr is 3D array, and by 

ptr1 = crr;

means, ptr1 is having BA of 0th 2D array of crr. and (ptr1 + 3) means jumping to 3rd 2D array. After that *(ptr1 + 3 ) means BA of 0th 1D array of 3rd 2D array. So, it should print BA of 0th 1D array of 3rd D array but it is directly printing the value which is stored at the BA of 0th 1D of 3rd 2D array.

why?

Comments

here....

ptr1 is a single int pointer....there for it will behace just like a simple pointer(poinmting to an element)

...let row major ordering is used then all the element od crr would be stored like this...

000

001

003

004.

....

now here ptr1 has starting address...and incerment in ptr1 will increment one by one as this is a int pointer.....

therefor it (ptr+3) will point ot 003 and it will print( 0+0+3)=3

Note:- ptr1 is 2-d pointer then ....it take all element of 3-d and consider as 2-d array..

Answer 1

Your analysis is partially correct, regarding ptr pointing to the 3rd 2D array,

ptr + 3 = ptr + (y * z * sizeof(int) * 3), where y and z are sizes of 2nd and 3rd dimension of crr (In our case, y = z = 5)

So, ptr + 3 = ptr + 5 * 5 * 3 * sizeof(int)

Since we can think memory as a linear array, the numbers are arranged as follows,

crr[0][0][0], crr[0][0][1], crr[0][0][2], crr[0][0][3], crr[0][0][4], crr[0][1][0] ...

Now, If you calculate the indices where ptr+ 3 points to, you can clearly see it is crr[3][0][0]

Since ptr is only a Single pointer (only one level of redirection is used)