i have this code to print a linklist [1,2,3]
void reverse(struct node *ptr){ head = ptr; while(ptr!=NULL){ printf("%d--->",ptr->data); ptr=ptr->next; } } output : 1-->2-->3
i am trying to print next element of ptr(current node) like
void reverse(struct node *ptr){ head = ptr; while(ptr!=NULL){ printf("%d--->",ptr->data); ptr=ptr->next; printf("%d--->",ptr->data); } } why is not printing 1-->2-->2-->3-->3 ?
You might like to change this
ptr=ptr->next; printf("%d--->",ptr->data); to become
ptr=ptr->next; if (NULL != ptr) printf("%d--->",ptr->data); For the last iteration the program tries to dereference NULL, which leads to undefined behaviour which in turn most propably makes the program crash then.
And as stdout is line buffered the buffer filled with 1-->2-->2-->3 will not be flushed and printed out anymore.
You might have a chance to reproduce this by adding
flush(stdout); after each call to print().
with the second code you will get a segmentation fault.
Because in this code
ptr=ptr->next; where ptr->next is NULL, then ptr will be NULL and then executing
printf("%d--->",ptr->data); with ptr = NULL will cause a segmentation fault
void reverse(struct node *ptr){ head = ptr; while(ptr!=NULL){ printf("%d--->",ptr->data); ptr=ptr->next; if (ptr) printf("%d--->",ptr->data); } } Try this code. The problem is that ptr will be equal to NULL at a moment during the loop, but you're doing printf("%d--->",ptr->data); just after the assignation of ptr. It's like : printf("%d--->",NULL->data); which leads to an undefined behavior (you will probably get a segmentation fault).
NULL->data? Do you understand this?