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+1 vote
q=head-> next;

A is the condition to see list is empty or not, which one is valid?

a) p!=NULL;

b) q!=NULL;





a) p!=NULL;

b) q!=NULL;



asked in Programming by Veteran (53.8k points)  
edited by | 115 views
Added the last part. Say what will be answer now and why?
Should be option B
how, explain in detail

Option B is correct.

If q!=Null then p is definitely not equal to Null.

The code must not enter the body of while loop if q=Null, this is because,

Observe this statement,

p = (p->next)? (p->next->next) : (p->next);

if at all p=Null then the condition (p->next) gives segmentation fault as it tries to access the next of Null.

@shreya here p moves one by one, while q moves two at a time whenever q is not pointing to last node... so if list will end q can detect it easily [q!=NULL] but the above code will work only if list has atleast one element..consider empty list... then p-> head [which is null for empty list] and q = head->next now while loop condition should give runtime error as q is saying to point next of NULL.

1 Answer

0 votes
List is empty means there would not be any node in the list. Means the pointer "head" should point to Null.

'q' will be considered if there exist atleast a single node. So all other three option will be eliminated.(As question is talking about empty list.)

Option A is correct.
answered by (37 points)  

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