Deleting node inside of linked list

问题

I'm stuck on this particular function that frees all even nodes from the linked list. I've figured out how to free all the nodes from a linked list but I cannot figure this out. The code i'm posting is very wrong. What I don't understand is how to use a node *temp variable and link it to the head->next node, as the head is what is being freed (because it is even). Also, at the end of the while loop, I know that I need to increment to the next node in the list, but I seem to be doing that already in the first if statement, so wouldn't calling current = current->next actually be taking me to current->next->next, and skipping a node? Sorry for this massive block of text.

node *delete_even_node(node *head)
{
    node *temp, *current = head;
    if (head == NULL)
        return NULL;
    while (current != NULL)
    {
        if (current->data % 2 == 0)
        {
            printf("Deleting Even %d\n", current->data);
            temp = current->next; //problem starts
            temp = temp->next;
            free(temp);
        }
        else
            current = current->next;
        current = current->next; 
    }
    return head;
}

回答1:

There are two approaches.

If to use your approach when the pointer to the head node is passed by value then the function can look the following way.

node * delete_even_node( node *head )
{
    while ( head && head->data % 2 == 0 )
    {
        node *tmp = head;
        head = head->next;
        free( tmp );
    }

    if ( head )
    {
        node *current = head;
        while ( current->next )
        {
            if ( current->next->data % 2 == 0 )
            {
                node *tmp = current->next;
                current->next = current->next->next;
                free( tmp );
            }
            else
            {
                current = current->next;
            }
        }
    }

    return head;
}

Another approach is to pass the pointer to the head node by reference.

For example

void delete_even_node( node **head )
{
    while ( *head )
    {
        if ( ( *head )->data % 2 == 0 )
        {
            node *tmp = *head;
            *head = ( *head )->next;
            free( tmp );
        }
        else
        {
            head = &( *head )->next;
        }
    }
}

And the function is called like

delete_even_node( &head );

来源：https://stackoverflow.com/questions/64527206/deleting-node-inside-of-linked-list