CODEWITHSUNDEEP
cdata-structurespriority-queue
Suvam Roy
Suvam Roy

Reputation: 953

Little confusion in Priority Queue in C

I've written the code like this:

ptr=front;
    while(ptr->link!=NULL && ptr->priority<itempriority ){
        ptr=ptr->link;
    }

    temp->link=ptr->link;
    ptr->link=temp;
    return front;

The above code didn't work.

  ptr=front;
        while(ptr->link!=NULL && ptr->link->priority<itempriority ){
            ptr=ptr->link;
        }

        temp->link=ptr->link;
        ptr->link=temp;
        return front;

This code worked perfectly.

I'm confused why my code was not working i.e. ptr->priority<itempriority ?

In short I want to know how ptr->link->priority<itempriority is working perfectly while ptr->priority<itempriority is not?

Upvotes: 1

Views: 65

Answers (1)

Gaurav Sehgal
Gaurav Sehgal

Reputation: 7542

Consider this 

1 -> 2 -> 5 -> 8

and you want to insert 3 at correct position

while(ptr->link!=NULL && ptr->priority<itempriority ){
        ptr=ptr->link;
    }

At the end, ptr will be pointing to 5.And finally you will have

1 -> 2 -> 5 -> 3 -> 8 //Wrong

The second version

while(ptr->link!=NULL && ptr->link->priority<itempriority ){
            ptr=ptr->link;
        }

At the end ptr will be 2, and finally

1 -> 2 -> 3 -> 5 -> 8 //correct

Upvotes: 4

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