CODEWITHSUNDEEP
c++
peter
peter

Reputation: 39

Linked list delete

template<typename T>
List<T>::~List()
{
    while(head->next !=NULL){
        delete head;
        head = head->next;
    }
    head = NULL;
}

I want to delete all the nodes in the linked list, but I don' t know why the code fail.

Upvotes: 1

Views: 109

Answers (4)

Pedro
Pedro

Reputation: 862

I would go with the following solution. No invalid memory access, no memory leak, and it automatically assigns NULL to head before leaving the loop:

template<typename T>
List<T>::~List()
{
    while (head)
    {
        Node<T> *next = head->next;
        delete head;
        head = next;
    }
}

Please note that I made a guess with the node type and you have to replace it by whatever is present in your code.

Upvotes: 1

Karol T.
Karol T.

Reputation: 653

It depends what type the head variable is. If it is the class, you can even use "recursive" deleting in "head" (I mean node) destructor. Something similar to:

Node::~Node(){
    if(this->next != nullptr)
        delete this->next;
    delete this->content;
}

If the node is internal struct, you need temporary pointer to next node as mentioned above:

template<typename T>
List<T>::~List()
{
    struct nodeType *temp;
    while(head != nullptr){
        temp = head->next;
        delete head;
        head = temp;
    }
}

In this case, you don't need to explicitly set head to null, since it is done by the logic of while loop.

In your loop (in question) you don't remove *head node, I don't know if it is expected behavior.

Ad. comment above (I can't put it directly): while(head->next!=NULL){ Node*next = head->next; delete head; head = next; } head = NULL; is wrong. It doesn't delete last node on the list (especially if the list has only one object, it won't be deleted).

Upvotes: 0

Bhawan
Bhawan

Reputation: 2491

This can help you in deleting every node of linked list.

   List<T> *current = head;
   while (current != NULL) 
   {
       next = current->next;
       delete current;
       current = next;
   }

Upvotes: 0

YSC
YSC

Reputation: 40060

Your code fails probably because it invokes undefined behaviour.

delete head;
head = head->next;

You cannot read the memory located where head points after having deleted head.

You should make a copy of head->next to reuse it:

const auto next = head->next;
delete head;
head = next;

Upvotes: 2

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