Question

I was going through the Programming Interviews Exposed book. There’s a code given for inserting an element at the front of linked lists.

bool insertInFront( IntElement **head, int data ){
    IntElement *newElem = new IntElement;
    if( !newElem ) return false;
    newElem->data = data;
    *head = newElem;
    return true;
}

IMHO this code forgets to update the next pointer of the new element, doesn’t it ? Although I am sure the code is wrong, I just want to confirm my linked list concepts are not horribly wrong.

I believe the code should add the following line at the right place.

newElem->next = *head;

Can someone please just tell me whether I am right or wrong ?

Answer 1

I’m not sure what kind of interview book you’re reading, but this code example is terrible c++.

Yes, you need to point newElem->next to the old head before overwriting head. Also, there’s no reason to check if newElem is NULL – if it couldn’t be allocated, C++ throws an exception. Also, insertInFront should be a member function of IntElement, and head should be a data member.