利用二级指针删除单向链表——笔记

//通常的写法
typedef struct node
{
    struct node * next;
    ....
} node;
 
typedef bool (* remove_fn)(node const * v);
 
// Remove all nodes from the supplied list for which the
// supplied remove function returns true.
// Returns the new head of the list.
node * remove_if(node * head, remove_fn rm)
{
    for (node * prev = NULL, * curr = head; curr != NULL; )
    {
        node * const next = curr->next;
        if (rm(curr))
        {
            if (prev)
                prev->next = next;
            else
                head = next;
            free(curr);
        }
        else
            prev = curr;
        curr = next;
    }
    return head;
}

//Linus所说的利用二级指针的写法。
void remove_if(node ** head, remove_fn rm)
{
    for (node** curr = head; *curr; )
    {
        node * entry = *curr;
        if (rm(entry))
        {
            *curr = entry->next;    //分离要删的节点
            free(entry);   //回收内存
        }
        else
            curr = &entry->next;   //->符号优先于&
    }
}