Remove all nodes in linked list

Question

I have a linked list contains 3 nodes like the image shown:

There is a head pointe

Answer 1

To delete all nodes except the first node, you can try below code.

temp1 = head->next;
while(temp1!=NULL) // as I am considering tail->next = NULL
{   
    head->next = temp1->next;
    temp1->next = NULL;
    free(temp1);
    temp1 = head->next;
}

This will delete all nodes except first one. But the data with the first node will remain as it is.

Answer 2

Instead of free, C++ uses delete function.

Check the link to have deep knowledge about all kind of operations(including recursive or iterative delete) on linked lists.

Answer 3

temp1 = head->next;

while(temp1!=NULL) // as I am considering tail->next = NULL
{
    head->next = temp1->next;
    temp1->next = NULL;
    free(temp1);
    temp1 = head->next;
}

The logic for this would be more correct if it is this way.

After the statement

free(temp1);

Add the condition

if (head -> next != NULL)
    temp1 = head->next;

Since after deleting the last node there is no point in reassigning the address of head pointer to temp1.

Answer 4

Disclaimer: I assume it's only for learning purposes and in real-world scenario you would use std::list<> or similar container.

For single-linked list, you can just drop all this burden an let the stdlib manage the pointers:

class Node {
    std::unique_ptr<Node> next;
};

You can safely use .reset() method to make operations on the list:

Given current_ptr, the pointer that was managed by *this, performs the following actions, in this order:

• Saves a copy of the current pointer old_ptr = current_ptr
• Overwrites the current pointer with the argument current_ptr = ptr
• If the old pointer was non-empty, deletes the previously managed object if(old_ptr != nullptr) get_deleter()(old_ptr).

_{From http://en.cppreference.com/w/cpp/memory/unique_ptr/reset.}

And that's pretty much what you would do when deleting. I believe you can also use unique_ptr::swap(), to easily manipulate your nodes.