How to print value from array using pointer to array

Question

Refer code below:

https://code.sololearn.com/cA106A12a114

How can I print value 12 using variable p1?

Answer 1

*( p1[ 0 ] + 1 ) prints 12.

Not sure what you're doing at line 15 though.

Answer 2

In your program, you are successfully able to print values of an array via a pointer pointing to it.

What's the issue then ?

Answer 3

Arsenic tank you.. issue was there but Ipang suggestions helped to come out of issue

Answer 4

Arsenic
Thank you so much! 🙏

I think I'd rather not use the (*ptr) way, it's rather confusing (for me at least).

Answer 5

Hey Ipang hope it will help you
&-this gives address of variable
* This is value at that address ( in pointers)

*(p1[0]+1) means
p1[0]=p1=base address of array
p1[0]+1= it means pointer now pointing to next element of array
*(p1[0]+1)=it means array next element value

Answer 6

No, we can't

By doing

int (*ptr)[2] = &arr;

We are declaring a single pointer which is meant to point at a data type of " int (*)[2] " which is an integer array of size 2 and making it point to the array "arr" which has to be of size 2 otherwise program will generate error.

Comparing it with

int *ptr = &arr;

Here the pointer "ptr" in meant to point to any integer value, and is currently pointing to first element of the array "arr" . The difference here is that, here unlike the other case, size of "arr" doesn't matter to pointer.

As of "p1[1]" is considered then this is the case of pointer arithmetic where "ptr[n]"
can be represented as (ptr + n*sizeof(data type it is pointing to) ) which means trying to acess p1[1] will lead to undefined behaviour.

Answer 7

Ipang it can be very useful, especially in case of using 2-D arrays where *(ptr[x] + y) can be used to access (x,y) element of the matrix.

Answer 8

Thank you... Creating a pointer which should point to array

Answer 9

So we store address of <arr> into <p1>. I suppose it is saved in index 0.

How do I save address of another array into <p1> at index 1?

Answer 10

Ipang , can we ? If yes , plz help me understand...

My current understanding is that P1 is just a pointer which has only one place holder which point to the arr of type int [2]

In other words , if arr[3] is there , it should have been int (*P1)[3]

Answer 11

No problem 👌
How do we assign an address for <p1>[1]?

Answer 12

Is it not same way what you suggested?

(p1[0] + 1)

Answer 13

I thought you mean to say that <p1> is a pointer that stores address of arrays (e.g. address of 2 array) 🙄

Answer 14

Hi Martin Taylor , does both p and p1 same ? If none of them is correct, could you please give propper example ?