雙鏈表本身不難，但是寫一個沒有錯誤的雙鏈表就有點難了，邊界條件要小心處理，不多說了，欣賞代碼吧
/*************************************************
?*???????????????????????????????????????????????*
?*??Module:?list.c???????????????????????????????*
?*??Description:?????????????????????????????????*
?*??????Simple?abstract?double?linked?list???????*
?*??Author:?Janssen,?T.H.,???????????????????????*
?*??????????Van?Oostenrijk,?A.C.?????????????????*
?*??Modifications:???????????????????????????????*
?*???????????????????????????????????????????????*
?*************************************************
?*???????????????????????????????????????????????*
?*???This?program?is?free?software;?you?can??????*
?*???redistribute?it?and/or?modify??it?under?????*
?*???the?terms?of?the?GNU?General?Public?????????*
?*???License?as?published?by?the?Free????????????*
?*???Software?Foundation;?either?version?2???????*
?*???of?the?License,?or?(at?your?option)?any?????*
?*???later?version.??????????????????????????????*
?*???????????????????????????????????????????????*
?*************************************************/

/*
?*?$Log:?list.c,v?$
?*?Revision?1.21??2003/01/10?10:30:48??dmeffert
?*?Fixed?segfault?bug?in?code?generation
?*
?*?Revision?1.20??2002/11/27?18:04:01??vanoostenrijk
?*?Added?more?comments?and?removed?all?routine?variables.?We?now?use?__FUNCTION__.
?*
?*?Revision?1.19??2002/11/27?15:14:58??jeeweee
?*?Improved?ListClear?function
?*
?*?Revision?1.18??2002/11/27?14:53:00??jeeweee
?*?Modified?ListClear?implementation?and?used?it?in?CheckFunctionHeader
?*
?*?Revision?1.17??2002/11/27?14:31:07??vanoostenrijk
?*?New?linked?list?code:?ListClear
?*
?*?Revision?1.16??2002/11/27?10:51:41??vanoostenrijk
?*?Added?line?numbers?to?AST.
?*
?*?Revision?1.15??2002/11/15?19:04:44??vanoostenrijk
?*?Wasted?many?hours?updating?header?comment?blocks.?Updated?header?template.
?*
?*?Revision?1.14??2002/11/15?18:41:05??vanoostenrijk
?*?Changed?all?tabs?I?could?find?to?4?spaces.
?*?Added?some?comments.
?*
?*?Revision?1.13??2002/11/15?18:21:06??vanoostenrijk
?*?Guys,?compile?with?-Wall!?Removed?as?many?warnings?as?I?could.
?*
?*?Revision?1.12??2002/11/14?19:43:17??vanoostenrijk
?*?Replaced?string?literals?with?macros?for?easy?translation?/?changing.
?*
?*?Revision?1.11??2002/11/14?17:29:30??vanoostenrijk
?*?Additional?code?for?extended?linked?list?operations.
?*
?*?Revision?1.10??2002/11/14?15:53:35??vanoostenrijk
?*?Added?new?linked?list?accessors,?restyled?code,?added?test?code.
?*
?*?Revision?1.9??2002/11/14?13:17:33??vanoostenrijk
?*?Added?code?for?tree?compaction.
?*
?*?Revision?1.8??2002/11/10?14:50:36??vanoostenrijk
?*?Cosmetic?changes.
?*
?*?Revision?1.7??2002/11/10?11:59:48??vanoostenrijk
?*?Fixed?some?warnings.
?*
?*?Revision?1.6??2002/11/07?10:11:50??tjanssen
?*?Added?missing?types.c
?*
?*?Revision?1.5??2002/10/17?13:16:23??tjanssen
?*?modified?header?again
?*
?*/

#include?<assert.h>
#include?<stdlib.h>
#include?<stdio.h>
#include?"list.h"
#include?"options.h"
#include?"defs.h"

/*************************************************
?*???????????????????????????????????????????????*
?*??STRINGS??????????????????????????????????????*
?*???????????????????????????????????????????????*
?*************************************************/

#define?ERR_LISTALLOC?"memory?allocation?for?new?list?failed\n"
#define?ERR_NODEALLOC?"failed?to?allocate?memory?for?new?node?in?list?%p\n"
#define?MSG_TEST?"Testing?list?ADT\n"
#define?MSG_LIST_ELEMENTS?"Listing?elements?(should?list?2x5?elements):?\n"
#define?MSG_LIST_ELEMENTS_1?"List?style?1:"
#define?MSG_LIST_ELEMENTS_2?"List?style?2:"
#define?MSG_REMOVED_ELEMENTS?"Removed?all?elements,?elements?left:"
#define?MSG_TEST_COMPLETE?"List?test?completed?successfully.\n\n"


//大部分操作都要小心處理雙鏈表操作的邊界條件，頭節點，尾節點，當前指針指向的節點

List?*ListInit(?DeleteFunction?deleteFunction?)
{
????List?*list;

????/*
?????*?Allocate?memory?for?list?structure.
?????*/
????list?=?(?List?*?)malloc(?sizeof(?List?)?);
????if?(?list?==?NULL?)
????{
????????BAILOUT(?ERR_LISTALLOC?);
????}

????/*
?????*?Initialize?new?list?structure.
?????*/
????list->deleteFunction?=?deleteFunction;??//注冊刪除節點用的回調函數
????list->first?=?list->last?=?list->current?=?NULL;

????return(?list?);
}

//調用deleteFunction來刪除所有節點，然后釋放list空間
void?ListPurge(?List?*list,?DeleteFunction?deleteFunction?)
{
????assert(?list?!=?NULL?);

????/*?Remove?items?one?by?one.?*/
????ListFirst(?list?);
????while?(?ListRemove(?list,?deleteFunction?)?)
????????;

????/*?Free?the?list?structure?itself.?*/
????free(?list?);
}

void?ListClear(?List?*list?)
{
????assert(?list?!=?NULL?);

????/*?Remove?items?one?by?one.?*/
????while(?ListSize(?list?)?>?0?)
????{
????ListLast(?list?);
????ListUnlink(?list?);
????}

????/*?Free?the?list?structure?itself.?*/
????free(?list?);
}


BOOL?ListInsert(?List?*list,?void?*data?)
{
????ListNode?*n,?*p,?*newNode;

????assert(?list?!=?NULL?);

????n?=?list->current;
????if?(?n?)
????{
????????p?=?n->prev;
????}
????else
????{
????????p?=?NULL;
????}

????newNode?=?(?ListNode?*?)malloc(?sizeof(?ListNode?)?);
????if?(?newNode?==?NULL?)
????{
????????BAILOUT(?ERR_NODEALLOC,?list?);?//輸出錯誤信息,?BAILOUT函數定義見文件defs.h
????}

????newNode->list?=?list;
????newNode->next?=?n;
????newNode->prev?=?p;
????newNode->data?=?data;

????/*?DEBUG(?"new[%p,%p,%p]\n",?newNode,?newNode->next,?newNode->prev?);?*/

????/*?fix?next?node?*/
????if?(?n?!=?NULL?)
????{
????????n->prev?=?newNode;
????}

????/*?fix?previous?node?*/
????if?(?p?!=?NULL?)
????{
????????p->next?=?newNode;
????}

????/*?if?null?or?next?fix?the?lists?first?ptr?*/
????//如果鏈表是空的，或者新插入的節點是第一個節點，則修正first指針
????if?(?list->first?==?NULL?||?list->first?==?newNode->next?)
????{
????????list->first?=?newNode;
????}

????/*?if?null,?fix?the?lists?last?ptr?*/
????//空鏈表
????if?(?list->last?==?NULL?)
????{
????????list->last?=?newNode;
????}

????/*?newly?inserted?node?becomes?current?ptr?*/
????list->current?=?newNode;????//current指向新插入的節點

????/*?DEBUG(?"f[%p],?l[%p],?c[%p]\n",?list->first,?list->last,?list->current?);?*/
????return(?TRUE?);
}

BOOL?ListAppend(?List?*list,?void?*data?)
{
????ListNode?*newNode;

????assert(?list?!=?NULL?);

????newNode?=?(?ListNode?*?)malloc(?sizeof(?ListNode?)?);
????if?(?!newNode?)
????{
????????BAILOUT(?ERR_NODEALLOC,?list?);
????}

????newNode->list?=?list;
????newNode->next?=?NULL;
????newNode->prev?=?list->last;
????newNode->data?=?data;

????if?(?list->last?!=?NULL?)???//非空鏈表
????{
????????list->last->next?=?newNode;
????}

????list->last?=?newNode;???//修正尾指針

????if?(?list->first?==?NULL?)??//空鏈表
????{
????????list->first?=?newNode;
????}

????if?(?list->current?==?NULL?)????//空鏈表
????{
????????list->current?=?newNode;
????}

????return(?TRUE?);
}

//去掉current指向的節點，但不釋放空間
void?*ListUnlink(?List?*list?)
{
????ListNode?*n,?*p,?*c;

????assert(?list?!=?NULL?);

????c?=?list->current;
????n?=?c->next;
????p?=?c->prev;

????/*?fix?first?or?last?ptr?if?either?was?removed?*/
????if?(?list->first?==?c?)
????{
????????list->first?=?n;
????}

????if?(?list->last?==?c?)
????{
????????list->last?=?p;
????}

????/*?take?out?the?node?by?altering?the?neighbours?*/
????if?(?p?!=?NULL?)
????{
????????p->next?=?n;
????}
????if?(?n?!=?NULL?)
????{
????????n->prev?=?p;
????}

????list->current?=?(n?!=?NULL)???n?:?p;

????return(?c?);
}

//刪除current指向的節點并釋放空間
BOOL?ListRemove(?List?*list,?DeleteFunction?deleteFunction?)
{
????ListNode?*n,?*p,?*c;

????assert(?list?!=?NULL?);

????if?(?list->current?==?NULL?)????//空鏈表
????{
????????return(?FALSE?);
????}

????c?=?list->current;
????n?=?c->next;
????p?=?c->prev;

????/*?fix?first?or?last?ptr?if?either?was?removed?*/
????if?(?list->first?==?c?)
????{
????????list->first?=?n;
????}

????if?(?list->last?==?c?)
????{
????????list->last?=?p;
????}

????/*?take?out?the?node?by?altering?the?neighbours?*/
????if?(?p?!=?NULL?)
????{
????????p->next?=?n;
????}
????if?(?n?!=?NULL?)
????{
????????n->prev?=?p;
????}

????/*?free?resources?held?by?data?ptr?*/
????if?(?c->data?!=?NULL)???//空間還沒有釋放
????{
????????if?(?deleteFunction?!=?NULL?)???//參數提供了刪除函數
????????{
????????????deleteFunction(?c->data?);??//調用參數提供的刪除函數來釋放空間
????????}
????????else?if?(?list->deleteFunction?!=?NULL?)????//參數沒有注冊刪除函數
????????{
????????????list->deleteFunction(?c->data?);????//調用初始化鏈表是注冊的刪除函數
????????}
????????else
????????{
????????????free(?c->data?);????//如果沒有注冊，也沒有提供刪除函數，則調用free來釋放空間
????????}
????}

????/*?remove?the?node?itself?*/
????free(?c?);??//是否自身結構體占用的空間

????list->current?=?(n?!=?NULL)???n?:?p;

????return(?TRUE?);
}

void?ListLast(?List?*list?)
{
????assert(?list?!=?NULL?);

????list->current?=?list->last;?//將current指向最后一個節點
}

void?ListFirst(?List?*list?)
{
????assert(?list?!=?NULL?);

????list->current?=?list->first;??//將current指向第一個節點
}

//current指向自己的后繼節點
void?ListNext(?List?*list?)
{
????assert(?list?!=?NULL?);

????if?(?list->current?!=?NULL?)
????{
????????list->current?=?list->current->next;
????}
}

//current指向自己的前驅節點
void?ListPrev(?List?*list?)
{
????assert(?list?!=?NULL?);

????if?(?list->current?!=?NULL?)
????{
????????list->current?=?list->current->prev;
????}
}

//返回current指向的節點的數據域(注：數據域是void?*指針)
void?*ListGet(?List?*list?)
{
????assert(?list?!=?NULL?);

????if?(?list->current?!=?NULL?)
????{
????????return(?list->current->data?);
????}

????return(?NULL?);
}

//返回鏈表元素個數
int?ListSize(?List?*list?)
{
????int?i?=?0;
????ListNode?*node;

????assert(?list?!=?NULL?);

????node?=?list->first;
????/*?DEBUG(?"f[%p],l[%p],c[%p]\n",?list->first,?list->last,?list->current?);?*/
????while?(?node?!=?NULL?)
????{
????????/*?DEBUG(?"iteration:?%d,self[%p],prev[%p],next[%p]->'%s'\n",?i,?n,?n->prev,?n->next,?(char?*)n->data?);??*/
????????i++;
????????node?=?node->next;
????};

????return(?i?);
}

/*************************************************
?*???????????????????????????????????????????????*
?*??EXTENDED?LINKED?LIST?FUNCTIONS???????????????*
?*???????????????????????????????????????????????*
?*************************************************/

ListNode?*ListFirstEx(?List?*list?)
{
????if(?list?==?NULL?)?return?NULL;
????return(?list->first?);
}

ListNode?*ListLastEx(?List?*list?)
{
????assert(?list?!=?NULL?);

????return(?list->last?);
}

ListNode?*ListNextEx(?ListNode?*node?)
{
????assert(?node?!=?NULL?);

????return(?node->next?);
}

ListNode?*ListPrevEx(?ListNode?*node?)
{
????assert(?node?!=?NULL?);

????return(?node->prev?);
}

//找到node指向的節點并刪除之
ListNode?*ListRemoveEx(?ListNode?*node?)
{
????ListNode?*next;

????next?=?node->next;

????ListFirst(?node->list?);
????while(?ListGet(?node->list?)?!=?node?)
????{
????????ListNext(?node->list?);
????}

????ListRemove(?node->list,?NULL?);

????return(?next?);
}

void?*ListUnlinkEx(?ListNode?*node?)
{
????ListFirst(?node->list?);
????while(?ListGet(?node->list?)?!=?node?)
????{
????????ListNext(?node->list?);
????}

????return(?ListUnlink(?node->list?)?);
}


//測試鏈表的各個操作
BOOL?TestList()
{
????List?*list;
????ListNode?*node;
????int?i;
????int?*a;

????fprintf(?stdout,?MSG_TEST?);

????/*?Create?a?new?linked?list.?*/
????list?=?ListInit(?NULL?);

????/*?Add?4?elements.?*/
????for(?i?=?1;?i?<?5;?i++?)
????{
????????a?=?(int?*)?malloc(?sizeof(?int?)?);
????????*a?=?i;
????????ListAppend(?list,?a?);
????}

????/*?Add?one?element?in?front.?*/
????a?=?(int?*)?malloc(?sizeof(?int?)?);
????*a?=?0;
????ListFirst(?list?);
????ListInsert(?list,?a?);

????/*?List?elements.?*/
????fprintf(?stdout,?MSG_LIST_ELEMENTS?);
????fprintf(?stdout,?MSG_LIST_ELEMENTS_1?);
????fprintf(?stdout,?"?["?);
????ListFirst(?list?);
????for(?i?=?0;?i?<?ListSize(?list?);?i++?)
????{
????????a?=?(?int?*?)?ListGet(?list?);
????????printf(?"%d,?",?*a?);
????????ListNext(?list?);
????}
????printf(?"]\n"?);

????fprintf(?stdout,?MSG_LIST_ELEMENTS_2?);
????fprintf(?stdout,?"?["?);
????node?=?ListFirstEx(?list?);
????while(?node?!=?NULL?)
????{
????????a?=?(?int?*?)?node->data;
????????printf(?"%d,?",?*a?);
????????node?=?ListNextEx(?node?);
????}
????printf(?"]\n"?);

????/*?Remove?all?elements.?*/
????while(?ListSize(?list?)?>?0?)
????{
????????ListFirst(?list?);
????????ListRemove(?list,?NULL?);
????}

????fprintf(?stdout,?MSG_REMOVED_ELEMENTS?);
????fprintf(?stdout,?"?["?);
????node?=?ListFirstEx(?list?);
????while(?node?!=?NULL?)
????{
????????a?=?(?int?*?)?node->data;
????????printf(?"%d,?",?*a?);
????????node?=?ListNextEx(?node?);
????}
????printf(?"]\n"?);

????fprintf(?stdout,?MSG_TEST_COMPLETE?);

????return(?TRUE?);
}

/*?EOF?*/