Консультация № 181267
13.12.2010, 00:37
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Здравствуйте, уважаемые эксперты! Прошу Вас помочь написать программу вставки и удаления элементов списка, используя для реализации списка двусвязный список.

Обсуждение

давно
Академик
20764
1861
13.12.2010, 08:24
общий
это ответ
Здравствуйте, Шаталов Виктор Олегович!
Слегка упрощённая реализация списка из ядра linux. Я её использовал в нескольких проектах на plain c. Компилятор - gcc.

Приложение:
/*!
* \file s_list.h
* Simple double linked list implementation.
* This is a simplified version of one from Linux kernel
*
* $Id: s_list.h 1229 2008-04-09 13:54:51Z xbatob $
*/

#ifndef _S_LIST_H
#define _S_LIST_H

/*
* Some of the internal functions ("__xxx") are useful when
* manipulating whole lists rather than single entries, as
* sometimes we already know the next/prev entries and we can
* generate better code by using them directly rather than
* using the generic single-entry routines.
*/

/*! \brief list head and list element */
struct list_head {
struct list_head *next; /*!< link to previous element */
struct list_head *prev; /*!< ink to next element */
};

#define LIST_HEAD_INIT(name) { &(name), &(name) }

/*! \brief declare (static) list head and initialize it */
#define LIST_HEAD(name) \
struct list_head name = LIST_HEAD_INIT(name)

/*! \brief initialize list head */
#define INIT_LIST_HEAD(ptr) \
(ptr)->next = (ptr); \
(ptr)->prev = (ptr);

/*
* Insert a new entry between two known consecutive entries.
*
* This is only for internal list manipulation where we know
* the prev/next entries already!
*/
static inline void __list_add(struct list_head * new,
struct list_head * prev,
struct list_head * next) {
new->next = next;
new->prev = prev;
prev->next = new;
next->prev = new;
}

/*!
* \brief add a new entry
* \param new new entry to be added
* \param head list head to add it after
*
* Insert a new entry after the specified head.
* This is good for implementing stacks.
*/
static inline void list_add(struct list_head *new, struct list_head *head) {
__list_add(new, head, head->next);
}

/*!
* \brief add a new entry
* \param new new entry to be added
* \param head list head to add it before
*
* Insert a new entry before the specified head.
* This is useful for implementing queues.
*/
static inline void list_add_tail(struct list_head *new, struct list_head *head) {
__list_add(new, head->prev, head);
}

/*
* Delete a list entry by making the prev/next entries
* point to each other.
*
* This is only for internal list manipulation where we know
* the prev/next entries already!
*/
static inline void __list_del(struct list_head * prev,
struct list_head * next) {
next->prev = prev;
prev->next = next;
}

/*!
* \brief deletes entry from list.
* \param entry the element to delete from the list.
*
* \note list_empty on entry does not return true after this,
* the entry is in an undefined state.
*/
static inline void list_del(struct list_head *entry) {
__list_del(entry->prev, entry->next);
}

/*!
* \brief deletes entry from list and reinitialize it.
* \param entry the element to delete from the list.
*/
static inline void list_del_init(struct list_head *entry) {
__list_del(entry->prev, entry->next);
INIT_LIST_HEAD(entry);
}

/*!
* \brief tests whether a list is empty
* \param head the list to test.
*/
static inline int list_empty(struct list_head *head) {
return head->next == head;
}

/*!
* \brief join two lists
* \param list the new list to add.
* \param head the place to add it in the first list.
*/
static inline void list_splice(struct list_head *list, struct list_head *head) {
struct list_head *first = list->next;

if (first != list) {
struct list_head *last = list->prev;
struct list_head *at = head->next;

first->prev = head;
head->next = first;

last->next = at;
at->prev = last;
}
}

/*!
* \brief get the struct for this entry
* \param ptr the &struct list_head pointer.
* \param type the type of the struct this is embedded in.
* \param member the name of the list_struct within the struct.
*/
#define list_entry(ptr, type, member) \
((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member)))

/*!
* \brief iterate over a list
* \param pos the &struct list_head to use as a loop counter.
* \param head the head for your list.
*/
#define list_for_each(pos, head) \
for (pos = (head)->next; pos != (head); \
pos = pos->next)

/*!
* \brief iterate over a list safe against removal of list entry
* \param pos the &struct list_head to use as a loop counter.
* \param n another &struct list_head to use as temporary storage
* \param head the head for your list.
* \note This construction is not safe if entries are also added
*/
#define list_for_each_safe(pos, n, head) \
for (pos = (head)->next, n = pos->next; pos != (head); \
pos = n, n = pos->next)

/*!
* \brief iterate over a list in reverse order
* \param pos the &struct list_head to use as a loop counter.
* \param head the head for your list.
*/
#define list_for_each_prev(pos, head) \
for (pos = (head)->prev; pos != (head); \
pos = pos->prev)


#endif /* #ifdef _S_LIST_H */
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