C / C++ / MFC

25-Aug-23 0:50

Code Segment (I) :

int dequeue() {
if (isFull(f)){
printf("Queue Underflow! Nothing
to Dequeue");
}
int dqd =f->data;
f = f->next;
return dqd;
}

Code Segment (II) :

int dequeue(){
int val=-1;
struct Node *ptr=f;
if(f==NULL){
printf("Empty\n");
}
else{
f=f->next;
val=ptr->data;
free(ptr);
return val;
}
}

In Code I, DeQueue operation is being carried out directly using front pointer.

In Code II, The same is happening but this time another Node pointer is created to store the front pointer.

So, What's is the Difference in these two methods!

CPallini25-Aug-23 1:36

25-Aug-23 1:36

Well...
The second one releases memory (while the first one does NOT relaase memory).

Moreover, in the first one, the

C++

if (isFull(f)){

line looks suspicious.

"In testa che avete, Signor di Ceprano?"
-- Rigoletto

ZAID razvi25-Aug-23 1:54

25-Aug-23 1:54

Sir, first code doesn't actually need to free something as it is not creating a node to perform operation rather doing the same thing using the front pointer directly.
And yes I have wrote a function 'isFull' already

CPallini25-Aug-23 2:10

25-Aug-23 2:10

Quote:
first code doesn't actually need to free something as it is not creating a node

Neither the second one is. So the second code wrongly releases memory.

Quote:
And yes I have wrote a function 'isFull' already

But you should check for not-empty condition, with is NOT quite the same of is-full, is it?

"In testa che avete, Signor di Ceprano?"
-- Rigoletto

ZAID razvi25-Aug-23 4:57

25-Aug-23 4:57

How is that possible sir! Second code is written by a renowned youtuber 'code_with_harry'. Okk, for your better understanding i'm pasting full source code here:

#include <stdio.h>
#include <stdlib.h>

struct Node *f = NULL;
struct Node *r = NULL;

struct Node{
int data;
struct Node *next;
};
void traversal(struct Node *f){
struct Node *ptr=f;
printf("------------\n");
while(ptr!=NULL){
printf("%d ",ptr->data);
ptr=ptr->next;
}
printf("\n------------\n");
}
int isEmpty(struct Node *f){
if (f == NULL){
return 1;
}
return 0;
}
int isFull(struct Node *f){
struct Node *n = (struct Node *)malloc(sizeof(struct Node));
if (n == NULL){
return 1;
}
return 0;
}
struct Node *enqueue(int val){
if (isFull(f)){
printf("Queue Overflow! Can't Enqueue %d\n", val);
return f;
}
else{
struct Node *n = (struct Node *)malloc(sizeof(struct Node));
n->data = val;
n->next = NULL;
if (isEmpty(f)){
f = r = n;
}
r->next = n;
r = n;
return f;
}
}
// int dequeue(){
// if (isFull(f)){
// printf("Queue Underflow! Nothing to Dequeue");
// }
// int dqd = f->data;
// f = f->next;
// return dqd;
// }
int dequeue(){
int val=-1;
struct Node *ptr=f;
if (f==NULL){
printf("Empty\n");
}
else{
f=f->next;
val=ptr->data;
free(ptr);
return val;
}
}
int main(){

enqueue(11);
enqueue(22);
enqueue(33);
enqueue(44);
traversal(f);

dequeue();
dequeue();
traversal(f);

return 0;
}

Richard Deeming28-Aug-23 21:34

Richard Deeming

28-Aug-23 21:34

ZAID razvi wrote:
Second code is written by a renowned youtuber

At least 90% of YouTube coding tutorial videos aren't worth the paper they're printed on.

And how do you know that this Harry is "renowned"? Is this something that other well-known, competent, and respected developers have said? Or is it an adjective he's applied to himself?

Either way, if the code doesn't work, there are two options: either you've made a mistake in copying it, or he made a mistake in writing it.

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

ZAID razvi28-Aug-23 21:52

28-Aug-23 21:52

Okay sir! Got your point, please calm down 😊

Andre Oosthuizen29-Aug-23 2:41

Andre Oosthuizen

29-Aug-23 2:41

Quote:
ouTube coding tutorial videos aren't worth the paper they're printed on.

Or the screen they are presented on.

Quote:
either you've made a mistake in copying it, or he made a mistake in writing it

Indeed, back to the drawing board.

Richard Deeming29-Aug-23 3:11

Richard Deeming

29-Aug-23 3:11

Andre Oosthuizen wrote:
Or the screen they are presented on.

That's the point - the screen they're presented on is worth much more than the paper they're (not) printed on. Big Grin | :-D

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

Richard MacCutchan28-Aug-23 21:56

Richard MacCutchan

28-Aug-23 21:56

ZAID razvi wrote:
written by a renowned youtuber 'code_with_harry'.

Believe that and you will believe anything. And if that is an example of his output I would say he is renowned for writing poor code.

Dave Kreskowiak29-Aug-23 2:04

Dave Kreskowiak

29-Aug-23 2:04

Harry is "renowned"? Prolific YouTube creator, maybe, but not renowned.

A 125 video series on "How to become a job ready programmer in 3 months"? BWAHAHAHAHA! That's bullshit, and everybody in this field knows it. He's got a sh*t-ton of self-promotion marketing, but that doesn't mean he can teach.

Asking questions is a skill
CodeProject Forum Guidelines
Google: C# How to debug code
Seriously, go read these articles.

Dave Kreskowiak

modified 30-Aug-23 9:59am.

Richard Deeming29-Aug-23 3:12

Richard Deeming

29-Aug-23 3:12

Dave Kreskowiak wrote:
that doesn't mean he can teach

Or even write code, from the sounds of it. Laugh | :laugh:

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

CPallini30-Aug-23 2:57

Invalid application of 'sizeof' to incomplete type 'struct Node'

30-Aug-23 2:57

Quote:
How is that possible sir! Second code is written by a renowned youtuber 'code_with_harry'.

I know. But here is renowed expert CPallini Big Grin | :-D

.
If you run Harry's code using Valgrind, then you get (something similar to)

==3144== LEAK SUMMARY:
==3144==    definitely lost: 64 bytes in 4 blocks
==3144==    indirectly lost: 0 bytes in 0 blocks
==3144==      possibly lost: 0 bytes in 0 blocks
==3144==    still reachable: 0 bytes in 0 blocks
==3144==         suppressed: 0 bytes in 0 blocks
==3144== 
==3144== For lists of detected and suppressed errors, rerun with: -s
==3144== ERROR SUMMARY: 4 errors from 4 contexts (suppressed: 0 from 0)

On the other hand, if you run the following, alternative code

#include <stdio.h>
#include <stdlib.h>


struct Node
{
  int val;
  struct Node * next;
};


void traversal(const struct Node * p)
{
  printf("------------\n");
  while (p)
  {
    printf("%d ",p->val);
    p = p->next;
  }
  printf("\n------------\n");
}

// isEmpty is not strictly needed
// isFull is meaning-less

struct Node * enqueue(struct Node *p, int val)
{

  struct Node * prev = NULL;
  while (p)
  {
    prev = p;
    p = p->next;
  }
  p = malloc(sizeof(struct Node ));
  if ( p )
  {
    p->val = val;
    p->next = NULL;
    if ( prev )
      prev->next = p;
  }
  return p;
}

int dequeue(struct Node ** pp)
{
  int val = -1;
  struct Node * p = *pp;
  if ( p )
  {
    val = p->val;
    *pp = p->next;
    free(p);
  }
  return val;
}

int main()
{
  struct Node * ph = enqueue(NULL, 11);
  enqueue(ph, 22);
  enqueue(ph, 33);
  enqueue(ph, 44);
  traversal(ph);
  dequeue(&ph);
  dequeue(&ph);
  traversal(ph);
  dequeue(&ph);
  dequeue(&ph);
  return 0;
}

then Valgrind is somewhat happier:

==3153== HEAP SUMMARY:
==3153==     in use at exit: 0 bytes in 0 blocks
==3153==   total heap usage: 5 allocs, 5 frees, 1,088 bytes allocated
==3153== 
==3153== All heap blocks were freed -- no leaks are possible
==3153== 
==3153== For lists of detected and suppressed errors, rerun with: -s
==3153== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

"In testa che avete, Signor di Ceprano?"
-- Rigoletto

ZAID razvi22-Aug-23 20:20

Re: Invalid application of 'sizeof' to incomplete type 'struct Node'

22-Aug-23 20:20

Cause of this error ?

Victor Nijegorodov22-Aug-23 20:41

Victor Nijegorodov

22-Aug-23 20:41

ZAID razvi wrote:
Cause of this error ?

Since you didn't provide any code snippets or problem description then:
error invalid application of 'sizeof' to incomplete type - Google Search

Re: Invalid application of 'sizeof' to incomplete type 'struct Node'

ZAID razvi24-Aug-23 23:45

Re: Invalid application of 'sizeof' to incomplete type 'struct Node'

24-Aug-23 23:45

Thanks for replying sir
The problem is solved
I'll let you know If encountered any other

CPallini22-Aug-23 21:06