DSA

[CPallini]

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 razvi]

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 #include 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 Deeming]

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 razvi]

Okay sir! Got your point, please calm down 😊

[Lost User]

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 Kreskowiak]

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 shit-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

[Andre Oosthuizen]

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 Deeming]

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. :-D

---

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

[Richard Deeming]

Dave Kreskowiak wrote:

that doesn't mean he can teach

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

---

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

[CPallini]

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 :-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
#include

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