C算法 ---链表
转载于http://blog.youkuaiyun.com/jsh13417/article/details/8297093?reload
链表是一种最为基础的数据结构,链表是由一组元素以一种特定的顺序组合或链接在一起的。在维护数据的集合时很有用途。在平时的数据处理过程中经常会会用链接进行数据的临时存储。但是如何才能使链表处理数据更加优化,下面简单介绍单链表处理情况!
1 、单链表介绍
单链表是各个元素之间通过一个指针彼此连接起来而组成的。元素可以分为2个部分:数据成员和一个称为nest的指针。通过这种2成员结构,将每个元素的next指针指向其元素后面的指针。为了更能描述这种结构可以看下图:
要访问链表中的元素,从链表的头部开始,通过next指针从一个元素到另一个元素。然而每个元素的都需要动态的申请和释放空间。元素和元素之间的连接关系可以确保每个元素都能够访问到。因为在对数据处理时,一定要特别的小心。如果中间丢失掉一个元素,后面的就无法访问到。
2 单链表的实现和分析
示例1 链表抽象的数据类型的头文件
- #ifndef LIST_H
- #define LIST_H
- #include <stdlib.h>
- /*define a structure for linked List elements */
- typedef struct ListElmt_{
- void *data;
- struct ListElmt_ *next;
- }ListElmt;
- /*define a structure for linked lists */
- typedef struct List_ {
- int size;
- int (*match)(constvoid * key1,constvoid * key2);
- void (*destroy)(void *data);
- ListElmt *head;
- ListElmt *tail;
- }List;
- /*Public Intefaces */
- void list_init(List *list,void (*destroy)(void *data));
- void list_destory(List *list);
- int list_ins_next(List *list, ListElmt *element,constvoid *data);
- int list_rem_next(List *list, ListElmt *element,void *data);
- #define list_size(list) ((list) -> size)
- #define list_head(list) ((list) -> head)
- #define list_tail(list) ((list) -> tail)
- #define list_is_head(list, element) ((element) == (list) -> head ? 1:0)
- #define list_is_tail(list, element) ((element) == (list) -> tail ? 1:0)
- #define list_data(element) ((element) -> data)
- #define list_next(element) ((element) -> next)
- #endif
示例2 链表抽象数据类型的实现
- #include <studio.h>
- #include <string.h>
- #include "../include/List.h"
- /*list_init */
- void list_init(List * list,void(* destroy)(void * data)) {
- /* initialize the list */
- list -> size = 0;
- list -> destroy = destroy;
- list -> head = NULL;
- list -> tail = NULL;
- return ;
- }
- /*list_destroy */
- void list_destory(List * list) {
- void *data;
- /*Remove eah element */
- while (list_size(list) > 0){
- if (list_rem_next(list, NULL, (void **) &data) == 0 && list -> destroy
- != NULL){
- /* Call a user-defined function to free dynamically allocated data*/
- list -> destroy(data);
- }
- }
- memset(list, 0, sizeof(List));
- return;
- }
- /*list_ins_nest */
- int list_ins_next (List * list, ListElmt * element,constvoid * data){
- ListElmt *new_element;
- /* Allocate storage for the element */
- if ((new_element = (ListElmt *)malloc(sizeof(ListElmt))) == NULL){
- return -1;
- }
- /*insert the element into the list */
- new_element ->data =(void *)data;
- if (element == NULL){
- /* handle insertion at the head of the list */
- if (list_size(list) == 0){
- list -> tail = new_element;
- }
- new_element ->next = list ->head;
- list -> head = new_element;
- } else {
- /*Handle insertion somewhere other than at the head */
- if (element ->next == NULL ){
- list ->tail = new_element;
- }
- new_element ->next = element ->next;
- element->next = new_element;
- }
- list->size ++;
- return 0;
- }
- /* list_rem_next */
- int list_rem_next(List * list, ListElmt * element,void * data) {
- ListElmt *old_element;
- /* Do not allow removal from an emptry list */
- if (list_size(list) == 0){
- return -1;
- }
- /* romove the element from the list */
- if (element == NULL){
- /* handle removel from the head of the list */
- *data = list->head->data;
- old_element = list ->head;
- list->head = list -> head->next;
- if (list_size(list) == 1){
- list->tail = NULL;
- }
- } else {
- /* handle removal from somewhere other than the head */
- if ( element->next == NULL){
- return -1;
- }
- *data = element->next->data;
- old_element = element->next;
- element->next = element->next->next;
- if (element ->next == NULL){
- list->tail = NULL;
- }
- }
- /* free the storage allocated by the abstract datatype*/
- free(old_element);
- list->size --;
- return 0;
- }
3 下面对几个重要的函数接口实现进行介绍
list_init
list_init用来初始化一个链表仪表能够执行其他的操作,主要成员的描述:
size:链表中元素的个数;初始化为0;
destroy:定义的一个析构函数(http://baike.baidu.com/view/1277985.htm);初始换有函数参数传入;
head和tail:2个指针主要表头和表尾。初始化为NULL;
list_destroy
list_destroy 用来销毁链表,也就是取出链表中的所有函数;
函数主要是循环判断size,直到size为0时退出。函数的实现是调用函数list_rem_next,第二个参数为NULL时,表示,从第一个元素开始删除。如果析构函数不为NULL,则应该调用析构函数。
list_ins_next
list_ins_next 将一个元素插入有element指定的元素之后。新元素的数据只想由用户传入的数据。想链表中插入数据要有2中情况要考虑:插入头或其他位置,具体参照函数的实现。当传入参数element为NULL,表示从插入到表头;
list_rem_next
list_rem_next 从链表中移除指定元素之后的那个节点,并将其保存的数据保存的参数data中;同样也需要考虑2中情况:删除头或者其他位置的。当参数element为NULL时,表示从表头删除!
4 双向链表
双向链表,如同名字所暗示的那样,链表元素之间由2个指针链接,双向链表中的每一个元素都有3部分组成:除了数据成员和指针next外,新增加了一个指针prev,指向其前驱元素的指针。下图清晰绘出双向链表的结构:
双向链表的实现和分析
- #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)(constvoid *key1,constvoid * key2);
- void (*destroy)(void *data);
- DlistElmt *head;
- DlistElmt *tail;
- }Dlist;
- /*Public Intefaces */
- void dlist_init(Dlist *dlist,void (*destroy)(void *data));
- void dlist_destory(Dlist *dlist);
- int dlist_ins_next(Dlist *dlist, DlistElmt *element,constvoid *data);
- int dlist_ins_prev(Dlist *dlist, DlistElmt *element,constvoid *data);
- int dlist_remove(Dlist *dlist, DlistElmt *element,void *data);
- #define dlist_size(dlist) ((dlist) ->size)
- #define dlist_head(dlist) ((dlist) ->head)
- #define dlist_tail(dlist) ((dlist) ->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 "../include/Dlist.h"
- /*dlist_init */
- void dlist_init(Dlist * dlist,void(* destroy)(void * data)){
- /* initialize the list */
- list -> size = 0;
- list -> destroy = destroy;
- list -> head = NULL;
- list -> tail = NULL;
- return ;
- }
- /*list_destroy */
- void dlist_destory(Dlist * dlist){
- void *data;
- /*Remove eah element */
- while (dlist_size(dlist) > 0){
- if (dlist_remove(dlist, dlist_tail(dlist), (void **) &data) == 0 && dlist -> destroy
- != NULL){
- /* Call a user-defined function to free dynamically allocated data*/
- dlist ->destroy(data);
- }
- }
- memset(dlist, 0, sizeof(Dlist));
- return;
- }
- /*dlist_destroy */
- void dlist_destory(Dlist * dlist) {
- void *data;
- /* remove each element */
- while (dlist_size(dlist) > 0){
- if (dlist_remove(Dlist * dlist, dlist_tail(dlist),void * data) == 0 &&
- dlist->destroy != NULL){
- /* call a user-defined function to free dynamically allocated data */
- dlist->destroy(data);
- }
- }
- memset(list,0,sizeof(Dlist));
- return;
- }
- /* dlist_ins_next */
- int dlist_ins_next(Dlist * dlist, DlistElmt * element,constvoid * data){
- DlistElmt *new_element;
- /* do not allow a NULL element unless dlist is empty*/
- if (element == NULL && dlist_size(dlist) == 0){
- return -1;
- }
- /* allocate storage for the element */
- if ((new_element = (DlistElmt *)malloc(sizeof(DlistElmt))) == NULL){
- return -1;
- }
- new_element->data = (void *) data;
- if (dlist_size(dlist) == 0){
- dlist->head = new_element;
- new_element->prev = NULL;
- new_element->next = NULL;
- dlist->tail = new_element;
- } else {
- new_element->next = element->next;
- new_element->prev = element;
- if (element->next == NULL){
- dlist->tail = new_element;
- } else {
- element->next->prev = new_element;
- }
- element->next = new_element;
- }
- dlist->size++;
- return 0;
- }
- int dlist_ins_prev(Dlist * dlist, DlistElmt * element,constvoid * data){
- DlistElmt *new_element;
- /* do not allow a NULL element unless dlist is empty*/
- if (element == NULL && dlist_size(dlist) == 0){
- return -1;
- }
- /* allocate storage for the element */
- if ((new_element = (DlistElmt *)malloc(sizeof(DlistElmt))) == NULL){
- return -1;
- }
- new_element->data = (void *) data;
- if (dlist_size(dlist) == 0){
- dlist->head = new_element;
- new_element->prev = NULL;
- new_element->next = NULL;
- dlist->tail = new_element;
- } else {
- new_element->next = element;
- new_element->prev = element->prev;
- if (element== NULL){
- dlist->tail = new_element;
- } else {
- element->prev->next= new_element;
- }
- element->prev = new_element;
- }
- dlist->size++;
- return 0;
- }
- int dlist_remove(Dlist * dlist, DlistElmt * element,void * data) {
- /*do not allow a NULL element or removal from an empty list */
- if (element == NULL || dlist_size(dlist) == 0){
- return -1;
- }
- /* Remove the element from the list */
- *data = element->data;
- if (element == dlist->head){
- /*handle removal from the head of the list */
- dlist->head = element->next;
- if (dlist->head ==NULL){
- dlist->tail = NULL;
- } else {
- element->next->prev = NULL;
- }
- } else {
- element->prev->next = element ->next;
- if (element->next == NULL){
- dlist->tail = element->prev;
- } else {
- element ->next->prev = element->prev;
- }
- }
- free(element);
- dlist->size--
- return 0;
- }
以上便是双向链表的函数实现过程,具体就不在分析了,和单向链表差不多!