双链表的实现
出自《算法精解：C語言描述》，dlist.c沒問題，但是在使用的demo上有些問題。
注意：原書有問題就是dlist_remove之后沒有free()。
相對而言，redis那種風格的刪除節點更好，因為是在函數體內釋放節點的，而不是外面。關于二者的比較參考：說透一級指針和二級指以及(void**)&在雙鏈表中的應用
整體來說，這本書中的代碼還是很精彩的：/*****************************************************************************
* *
* ------------------------------- dlist.h -------------------------------- *
* *
*****************************************************************************/#ifndef DLIST_H
#define DLIST_H#include <stdlib.h>/*****************************************************************************
* *
* Define a structure for doubly-linked list elements. *
* *
*****************************************************************************/typedef struct DListElmt_ {void *data;
struct DListElmt_ *prev;
struct DListElmt_ *next;} DListElmt;/*****************************************************************************
* *
* Define a structure for doubly-linked lists. *
* *
*****************************************************************************/typedef struct DList_ {int size;int (*match)(const void *key1, const void *key2);
void (*destroy)(void *data);DListElmt *head;
DListElmt *tail;} DList;/*****************************************************************************
* *
* --------------------------- Public Interface --------------------------- *
* *
*****************************************************************************/void dlist_init(DList *list, void (*destroy)(void *data));void dlist_destroy(DList *list);int dlist_ins_next(DList *list, DListElmt *element, const void *data);int dlist_ins_prev(DList *list, DListElmt *element, const void *data);int dlist_remove(DList *list, DListElmt *element, void **data);#define dlist_size(list) ((list)->size)#define dlist_head(list) ((list)->head)#define dlist_tail(list) ((list)->tail)#define dlist_is_head(element) ((element)->prev == NULL ? 1 : 0)#define dlist_is_tail(element) ((element)->next == NULL ? 1 : 0)#define dlist_data(element) ((element)->data)#define dlist_next(element) ((element)->next)#define dlist_prev(element) ((element)->prev)#endif
/*****************************************************************************
* *
* ------------------------------- dlist.c -------------------------------- *
* *
*****************************************************************************/#include <stdlib.h>
#include <string.h>#include "dlist.h"/*****************************************************************************
* *
* ------------------------------ dlist_init ------------------------------ *
* *
*****************************************************************************/void dlist_init(DList *list, void (*destroy)(void *data)) {/*****************************************************************************
* *
* Initialize the list. *
* *
*****************************************************************************/list->size = 0;
list->destroy = destroy;
list->head = NULL;
list->tail = NULL;return;}/*****************************************************************************
* *
* ---------------------------- dlist_destroy ----------------------------- *
* *
*****************************************************************************/void dlist_destroy(DList *list) {void *data;/*****************************************************************************
* *
* Remove each element. *
* *
*****************************************************************************/while (dlist_size(list) > 0) {if (dlist_remove(list, dlist_tail(list), (void **)&data) == 0 && list->destroy != NULL) {/************************************************************************ ** Call a user-defined function to free dynamically allocated data. ** ************************************************************************/list->destroy(data);}}/*****************************************************************************
* *
* No operations are allowed now, but clear the structure as a precaution. *
* *
*****************************************************************************/memset(list, 0, sizeof(DList));return;}/*****************************************************************************
* *
* ---------------------------- dlist_ins_next ---------------------------- *
* *
*****************************************************************************/int dlist_ins_next(DList *list, DListElmt *element, const void *data) {DListElmt *new_element;/*****************************************************************************
* *
* Do not allow a NULL element unless the list is empty. *
* *
*****************************************************************************/if (element == NULL && dlist_size(list) != 0)return -1;/*****************************************************************************
* *
* Allocate storage for the element. *
* *
*****************************************************************************/if ((new_element = (DListElmt *)malloc(sizeof(DListElmt))) == NULL)return -1;/*****************************************************************************
* *
* Insert the new element into the list. *
* *
*****************************************************************************/new_element->data = (void *)data;if (dlist_size(list) == 0) {/*************************************************************************** ** Handle insertion when the list is empty. ** ***************************************************************************/list->head = new_element;list->head->prev = NULL;list->head->next = NULL;list->tail = new_element;}else {/*************************************************************************** ** Handle insertion when the list is not empty. ** ***************************************************************************/new_element->next = element->next;new_element->prev = element;if (element->next == NULL)list->tail = new_element;elseelement->next->prev = new_element;element->next = new_element;}/*****************************************************************************
* *
* Adjust the size of the list to account for the inserted element. *
* *
*****************************************************************************/list->size++;return 0;}/*****************************************************************************
* *
* ---------------------------- dlist_ins_prev ---------------------------- *
* *
*****************************************************************************/int dlist_ins_prev(DList *list, DListElmt *element, const void *data) {DListElmt *new_element;/*****************************************************************************
* *
* Do not allow a NULL element unless the list is empty. *
* *
*****************************************************************************/if (element == NULL && dlist_size(list) != 0)return -1;/*****************************************************************************
* *
* Allocate storage to be managed by the abstract data type. *
* *
*****************************************************************************/if ((new_element = (DListElmt *)malloc(sizeof(DListElmt))) == NULL)return -1;/*****************************************************************************
* *
* Insert the new element into the list. *
* *
*****************************************************************************/new_element->data = (void *)data;if (dlist_size(list) == 0) {/*************************************************************************** ** Handle insertion when the list is empty. ** ***************************************************************************/list->head = new_element;list->head->prev = NULL;list->head->next = NULL;list->tail = new_element;}else {/*************************************************************************** ** Handle insertion when the list is not empty. ** ***************************************************************************/new_element->next = element; new_element->prev = element->prev;if (element->prev == NULL)list->head = new_element;elseelement->prev->next = new_element;element->prev = new_element;}/*****************************************************************************
* *
* Adjust the size of the list to account for the new element. *
* *
*****************************************************************************/list->size++;return 0;}/*****************************************************************************
* *
* ----------------------------- dlist_remove ----------------------------- *
* *
*****************************************************************************/int dlist_remove(DList *list, DListElmt *element, void **data) {/*****************************************************************************
* *
* Do not allow a NULL element or removal from an empty list. *
* *
*****************************************************************************/if (element == NULL || dlist_size(list) == 0)return -1;/*****************************************************************************
* *
* Remove the element from the list. *
* *
*****************************************************************************/*data = element->data;if (element == list->head) {/*************************************************************************** ** Handle removal from the head of the list. ** ***************************************************************************/list->head = element->next;if (list->head == NULL)list->tail = NULL;elseelement->next->prev = NULL;}else {/*************************************************************************** ** Handle removal from other than the head of the list. ** ***************************************************************************/element->prev->next = element->next;if (element->next == NULL)list->tail = element->prev;elseelement->next->prev = element->prev;}/*****************************************************************************
* *
* Free the storage allocated by the abstract data type. *
* *
*****************************************************************************/free(element);/*****************************************************************************
* *
* Adjust the size of the list to account for the removed element. *
* *
*****************************************************************************/list->size--;return 0;}
/*****************************************************************************
* *
* ex-1.c *
* ====== *
* *
* Description: Illustrates using a doubly-linked list (see Chapter 5). *
* *
*****************************************************************************/#include <stdio.h>
#include <stdlib.h>#include "dlist.h"/*****************************************************************************
* *
* ------------------------------ print_list ------------------------------ *
* *
*****************************************************************************/void print_list(const DList *list) {DListElmt *element;int *data,i;/*****************************************************************************
* *
* Display the doubly-linked list. *
* *
*****************************************************************************/fprintf(stdout, "List size is %d\n", dlist_size(list));i = 0;
element = dlist_head(list);while (1) {data = dlist_data(element);fprintf(stdout, "list[%03d]=%03d\n", i, *data);i++;if (dlist_is_tail(element))break;elseelement = dlist_next(element);}return;}/*****************************************************************************
* *
* --------------------------------- main --------------------------------- *
* *
*****************************************************************************/int main(int argc, char **argv) {DList list;
DListElmt *element;int *data,i;/*****************************************************************************
* *
* Initialize the doubly-linked list. *
* *
*****************************************************************************/dlist_init(&list, free);/*****************************************************************************
* *
* Perform some doubly-linked list operations. *
* *
*****************************************************************************/element = dlist_head(&list);for (i = 10; i > 0; i--) {if ((data = (int *)malloc(sizeof(int))) == NULL)return 1;*data = i;if (dlist_ins_prev(&list, dlist_head(&list), data) != 0)return 1;}print_list(&list);element = dlist_head(&list);for (i = 0; i < 8; i++)element = dlist_next(element);data = dlist_data(element);
fprintf(stdout, "Removing an element after the one containing %03d\n", *data);if (dlist_remove(&list, element, (void **)&data) != 0)return 1;print_list(&list);fprintf(stdout, "Inserting 011 at the tail of the list\n");*data = 11;
if (dlist_ins_next(&list, dlist_tail(&list), data) != 0)return 1;print_list(&list);fprintf(stdout, "Removing an element at the tail of the list\n");element = dlist_tail(&list);
if (dlist_remove(&list, element, (void **)&data) != 0)return 1;print_list(&list);fprintf(stdout, "Inserting 012 just before the tail of the list\n");*data = 12;
if (dlist_ins_prev(&list, dlist_tail(&list), data) != 0)return 1;print_list(&list);fprintf(stdout, "Iterating and removing the fourth element\n");element = dlist_head(&list);
element = dlist_next(element);
element = dlist_prev(element);
element = dlist_next(element);
element = dlist_prev(element);
element = dlist_next(element);
element = dlist_next(element);
element = dlist_next(element);if (dlist_remove(&list, element, (void **)&data) != 0)return 1;print_list(&list);fprintf(stdout, "Inserting 013 before the first element\n");*data = 13;
if (dlist_ins_prev(&list, dlist_head(&list), data) != 0)return 1;print_list(&list);fprintf(stdout, "Removing an element at the head of the list\n");if (dlist_remove(&list, dlist_head(&list), (void **)&data) != 0)return 1;print_list(&list);fprintf(stdout, "Inserting 014 just after the head of the list\n");
*data = 14;if (dlist_ins_next(&list, dlist_head(&list), data) != 0)return 1;print_list(&list);fprintf(stdout, "Inserting 015 two elements after the head of the list\n");if ((data = (int *)malloc(sizeof(int))) == NULL)return 1;*data = 15;
element = dlist_head(&list);
element = dlist_next(element);if (dlist_ins_next(&list, element, data) != 0)return 1;print_list(&list);i = dlist_is_head(dlist_head(&list));
fprintf(stdout, "Testing dlist_is_head...Value=%d (1=OK)\n", i);
i = dlist_is_head(dlist_tail(&list));
fprintf(stdout, "Testing dlist_is_head...Value=%d (0=OK)\n", i);
i = dlist_is_tail(dlist_tail(&list));
fprintf(stdout, "Testing dlist_is_tail...Value=%d (1=OK)\n", i);
i = dlist_is_tail(dlist_head(&list));
fprintf(stdout, "Testing dlist_is_tail...Value=%d (0=OK)\n", i);/*****************************************************************************
* *
* Destroy the doubly-linked list. *
* *
*****************************************************************************/fprintf(stdout, "Destroying the list\n");
dlist_destroy(&list);return 0;}
實現流程
下面是一個網友寫的demo，修正了原demo中remove后沒有free的問題，可以參考：
/** filename:main.c* author:zhm* date:2012-12-08*/#include<stdio.h>
#include<stdlib.h>
#include<string.h>#include "dlist.h"typedef struct Cuboid_
{int length;int width;int height;
}Cuboid;Cuboid *cube_instance(const int length, const int width, const int height)
{Cuboid *cb_ptr;cb_ptr = (Cuboid *)malloc(sizeof(Cuboid));if( cb_ptr == NULL )return NULL;cb_ptr->length = length;cb_ptr->width = width;cb_ptr->height = height;return cb_ptr;
}/*destroy */
void destroy(void *data)
{free(data);return;
}/* main */
int main(int argc, char **argv)
{int i;DList dlist_exp;DListElmt *p = NULL;Cuboid *cb1_ptr, *cb2_ptr, *cb3_ptr, *cb4_ptr, *cb5_ptr;Cuboid *cb_ptr;//cb1_ptr ~ cb5_ptr are the data of the 5 elements.cb1_ptr = cube_instance(1,2,3);cb2_ptr = cube_instance(6,10,8);cb3_ptr = cube_instance(5,20,30);cb4_ptr = cube_instance(17,100,25);cb5_ptr = cube_instance(3,6,9);//init the double linked list.dlist_init(&dlist_exp, destroy);//insert the 5 elements into the dlist dlist_ins_next(&dlist_exp, NULL, (void *)cb1_ptr ); //insert data:cb1p = dlist_head(&dlist_exp); //get the address of the first elementdlist_ins_next(&dlist_exp, p , (void *)cb2_ptr ); //insert data:cb2 cb1- cb2p = dlist_next(p); //pointer to the element containing the data cb2.dlist_ins_prev(&dlist_exp, p, (void *)cb3_ptr ); //insert data:cb3 cb1- cb3- cb2dlist_ins_prev(&dlist_exp, p, (void *)cb4_ptr ); //insert data:cb4 cb1- cb3- cb4- cb2p = dlist_prev(p); //pointer to the element conatining the data cb4.dlist_ins_prev(&dlist_exp, p, (void *)cb5_ptr ); //insert data:cb5 cb1- cb3- cb5- cb4- cb2//now the sequence is: head->cb1->cb3->cb5->cb4->cb2printf("traverse and print:\n");p = dlist_head(&dlist_exp); //get the head element;for( i = 0; i < dlist_size(&dlist_exp); i++ ){cb_ptr = (Cuboid *)dlist_data(p); //get the element's data, every data is a Cuboid's pointer.printf("i = %d: ",i);printf("length = %d, width = %d, height = %d\n",cb_ptr->length,cb_ptr->width,cb_ptr->height);p = dlist_next(p); //pointer to next element;}//we'll remove the third element:that's containing the data of cb5(3,6,9)p = dlist_head(&dlist_exp);p = dlist_next(p);p = dlist_next(p);dlist_remove(&dlist_exp, p, (void **)&cb_ptr);printf("the data of the third element: length = %d, width = %d, height = %d\n",cb_ptr->length,cb_ptr->width,cb_ptr->height);destroy(cb_ptr); //free the memory//now we'll show you the remained elements,the sequence is :(head)cb1->cb3->cb4->cb2(tail)printf("after remove the third elements:\n");p = dlist_head(&dlist_exp);for(i = 0; i < dlist_size(&dlist_exp); i++ ){cb_ptr = (Cuboid *)dlist_data(p);printf("i = %d: ",i);printf("length = %d, width = %d, height = %d\n",cb_ptr->length,cb_ptr->width,cb_ptr->height);p = dlist_next(p);}//destroy the double linked listdlist_destroy(&dlist_exp);printf("after destroy the list,its size = %d\n", dlist_size(&dlist_exp));return 0;
}
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