一、线性表及其分类
（定义部分参考自《大话数据结构》及维基百科）
线性表(List / Linear List)：零个或多个数据元素的有限序列。
线性表的基本操作（涉及算法中方法实现）：
线性表初始化；
求线性表长度；
获取元素操作；
查找元素操作；
插入元素操作；
删除元素操作；
其他：判断线性表是否为空；清空线性表；
线性表可以存储结构特点分为两类：
1.顺序表 Sequence List（线性表的顺序存储结构）：用一段地址连续的存储单元一次存储线性表的数据元素。
根据存储单元的内存开辟方式可以分为（根据不同的需求顺序表可以按照以下不同的方式实现）：
1.1静态顺序表：保存数据元素的内存是在程序编译时就开辟的，空间大小是静态的。（针对C语言：可由数组实现。）
1.2动态顺序表：保存数据元素的内存是在程序运行时才开辟的，空间大小是动态的。（针对C语言：可由标准函数malloc和free动态实现。）
2.链表 Linked List（线性表的链式存储结构）：由n个结点链结成的链表。
根据结点(node)的内存开辟方式可以分为（根据不同的需求链表可以按照以下不同的方式实现）：
2.1.1静态链表：保存结点的内存是在程序编译时就开辟的，空间大小是静态的。（针对C语言：可由数组实现。）
2.1.2动态链表：保存结点的内存是在程序运行时才开辟的，空间大小是动态的。（针对C语言：可由标准函数malloc和free动态实现。）
根据结点(node)中存储逻辑关系的数据特征分类，常见有下面三种（根据不同的需求链表可以按照以下不同的方式实现）：
（单链接或双链接，已排序或未排序，循环或非循环）
2.2.1单链表(singly linked list) ：每个对象含关键字和后继指针
2.2.2双向链表(doubly linked list)：每个对象含关键字，前驱指针和后继指针
2.2.3循环链表(circular linked list)（也可再分为单循环链表和双循环链表）：首尾对象含有指针指向，形成圆环。
（上述更详细分类和术语可参考： http://zh.wikipedia.org/wiki/线性表http://en.wikipedia.org/wiki/Linked_list）
分析：对于线性表这一数据结构的分类，不同的作者有不同的分类方法，这里我采用我认为相对比较科学全面的分类方式，也尽量避免这些术语乱用。这些分类方式首先是脱离具体的程序设计语言去定义的，接着算法再利用特定的程序设计语言进行实现。我这边主要用C语言实现这些链表的数据结构和方法，供以后使用。
顺序表和链表优缺点比较：
顺序表：
优点： 随机存取时间复杂度为O(1)；无需为表中元素之间的逻辑关系额外增加存储空间
缺点： 插入、删除操作需要移动大量的元素，时间复杂度为O(n)；表的长度难以确定
链表：
优点： 插入、删除节点时不移动数据， 效率高，时间复杂度为O（1）
缺点： 存取时要遍历，效率低，时间复杂度为O(n)
因此，综上所诉，顺序存储结构适合频繁存取、查找，很少插入、删除的情况；链式存储适合频繁插入、删除，很少存取的情况；
二、线性表C实现
目标：
1.实现大多数类型的线性表数据结构，用于其他算法调用，以后需要使用现在未实现的线性表时在逐步加入；
2.算法具有通用，高效，简洁，注释充分四个特点，便于进行其他程序设计语言移植；
特点：
1.所有线性表的文件含有共用的文件头(list.h)（主要是通用的宏定义和标准函数库头文件包含，避免重复定义，方便维护）；
2.由于不同类型的线性表使用的结构体名和函数名可能一致，各自含有相应的头文件(*.h)和实现文件(*.c)，C语言不具有函数重载功能，因此只能独立使用这些线性表的数据类型（优点是避免因类型过多导致结构体名和函数名命名较乱，缺点是不能够在同一个文件中同时使用）；
3.实现各个类型的线性表的基本操作。
注意：
1.实现线性表基本操作时函数的返回值值得考究，这里原则上尽量减少不必要返回值。
2.实现线性表基本操作时函数的返回状态可以用枚举类型实现（未实现）。
3.断言语句(assert)的参数需要认真考虑。
汇总：
头文件(list.h)：
/** * @file list.h * @brief list header that has macro definition used by many types of list. * @author chenxilinsidney * @version 1.0 * @date 2015-01-19 */ #ifndef __LIST_H__ #define __LIST_H__ #include <stdio.h> #include <stdlib.h> #include <string.h> // #define NDEBUG #include <assert.h> /// list return state #ifndef OK #define OK 1 #endif #ifndef ERROR #define ERROR 0 #endif #ifndef TRUE #define TRUE 1 #endif #ifndef FALSE #define FALSE 0 #endif /// list array maz length used by static sequence list, can be modified #define LIST_MAXSIZE 1000 /// list initialize size used by dynamic sequence list, can be modified #define LIST_INIT_SIZE 1000 /// list memory increated size used by dynamic sequence list, can be modified #define LIST_INCREMENT 2 /// data type, can be modified typedef int Status; ///< status data type typedef int ElementType; ///< element data type typedef int CommonType; ///< common data type #endif // __LIST_H__
静态顺序表(sequence_list_satic.h sequence_list_static.c)：
/**
* @file sequence_list_static.h
* @brief static sequence list header.
* @author chenxilinsidney
* @version 1.0
* @date 2015-01-19
*/
#ifndef __SEQUENCE_LIST_STATIC_H__
#define __SEQUENCE_LIST_STATIC_H__
#include "list.h"
/// static sequence list structure
typedef struct {
ElementType data[LIST_MAXSIZE]; ///< list elements
CommonType length; ///< list length
}SqList;
/// static sequence list method
/// initialize list
void InitList(SqList* L);
/// detect if list is empty
Status ListEmpty(SqList* L);
/// clear list
void ClearList(SqList* L);
/// get list length
CommonType ListLength(SqList* L);
/// get element from the list
Status GetElem(SqList* L, CommonType index, ElementType* e);
/// locate element of the index
CommonType LocateElem(SqList* L, ElementType e);
/// insert element to the list
Status ListInsert(SqList* L, CommonType index, ElementType e);
/// delete element from the list
Status ListDelete(SqList* L, CommonType index, ElementType* e);
#endif // __SEQUENCE_LIST_STATIC_H__
/**
* @file sequence_list_static.c
* @brief static sequence list method implements.
* The methods use <assert.h> to help debug the program.
* @author chenxilinsidney
* @version 1.0
* @date 2015-01-19
*/
#include "sequence_list_static.h"
/**
* @brief initialize the list.
*
* @param[in,out] L list struct pointer
*
*/
void InitList(SqList* L)
{
assert(L != NULL);
/// initialize length only, ignore the list data
L->length = 0;
}
/**
* @brief detect if the list is empty.
*
* @param[in] L list struct pointer
*
* @return return TRUE if empty, else return FALSE
*/
Status ListEmpty(SqList* L)
{
assert(L != NULL && L->length >= 0);
/// always have length >= 0
if (L->length)
return FALSE;
else
return TRUE;
}
/**
* @brief clear the list.
*
* @param[in,out] L list struct pointer
*
*/
void ClearList(SqList* L)
{
assert(L != NULL);
/// set length only, ignore the list data
L->length = 0;
}
/**
* @brief get list length.
*
* @param[in] L list struct pointer
*
* @return list length
*/
CommonType ListLength(SqList* L)
{
assert(L != NULL && L->length >= 0);
return L->length;
}
/**
* @brief get element from the list.
*
* @param[in] L list struct pointer
* @param[in] index the index from the list
* @param[out] e the element by index
*
* @warning index begin from 1
*
* @return return OK if success, else return ERROR
*/
Status GetElem(SqList* L, CommonType index, ElementType* e)
{
assert(L != NULL && e != NULL && L->length >= 0);
/// index should be in reasonable range
if (index > L->length || index < 1)
return ERROR;
/// get element from list
*e = L->data[index - 1];
return OK;
}
/**
* @brief locate element by index.
*
* @param[in] L list struct pointer
* @param[in] e the element to be located
*
* @warning index begin from 1
*
* @return return the index of the element if success, else return 0
*/
CommonType LocateElem(SqList* L, ElementType e)
{
assert(L != NULL && L->length >= 0);
CommonType i;
for (i = 1; i <= L->length; i++)
if (L->data[i - 1] == e)
/// get index of the first found element from list
return i;
return 0;
}
/**
* @brief insert element to the list at given index.
*
* @param[in,out] L list struct pointer
* @param[in] index the index from the list
* @param[in] e the element to be insert
*
* @warning index begin from 1
*
* @return return OK if success, else return ERROR
*/
Status ListInsert(SqList* L, CommonType index, ElementType e)
{
assert(L != NULL && L->length >= 0);
/// list length and index should be in reasonable range
if (L->length == LIST_MAXSIZE || index > (L->length + 1) || index < 1)
return ERROR;
/// move the element after the index position to next position
CommonType i;
for (i = L->length - 1; i >= index - 1; i--)
L->data[i + 1] = L->data[i];
/// increase list length
L->length++;
/// insert element
L->data[index - 1] = e;
return OK;
}
/**
* @brief delete element from the list.
*
* @param[in,out] L list struct pointer
* @param[in] index the index from the list
* @param[out] e the element to be deleted
*
* @warning index begin from 1
*
* @return return OK and set e if success, else return ERROR
*/
Status ListDelete(SqList* L, CommonType index, ElementType* e)
{
assert(L != NULL && e != NULL && L->length >= 0);
/// index should be in reasonable range
if (index > L->length || index < 1)
return ERROR;
/// get deleted element
*e = L->data[index - 1];
/// move the element after the index position to previous position
CommonType i;
for (i = index; i < L->length; i++)
L->data[i - 1] = L->data[i];
/// decrease list length
L->length--;
return OK;
}
动态顺序表(sqlist_dynamic.h sqlist_dynamic.c)：
/**
* @file sequence_list_dynamic.h
* @brief dynamic sequence list header.
* @author chenxilinsidney
* @version 1.0
* @date 2015-01-19
*/
#ifndef __SEQUENCE_LIST_DYNAMIC_H__
#define __SEQUENCE_LIST_DYNAMIC_H__
#include "list.h"
/// dynamic sequence list structure
typedef struct {
ElementType* data; ///< list elements
CommonType length; ///< list length
CommonType listsize; ///< list size mallocated
}SqList;
/// dynamic sequence list method
/// initialize list
void InitList(SqList* L);
/// destroy list
void DestroyList(SqList* L);
/// detect if list is empty
Status ListEmpty(SqList* L);
/// clear list
void ClearList(SqList* L);
/// get list length
CommonType ListLength(SqList* L);
/// get element from the list
Status GetElem(SqList* L, CommonType index, ElementType* e);
/// locate element of the index
CommonType LocateElem(SqList* L, ElementType e);
/// insert element to the list
Status ListInsert(SqList* L, CommonType index, ElementType e);
/// delete element from the list
Status ListDelete(SqList* L, CommonType index, ElementType* e);
#endif // __SEQUENCE_LIST_DYNAMIC_H__
/**
* @file sequence_list_dynamic.c
* @brief dynamic sequence list method implements.
* The methods use <assert.h> to help debug the program.
* @author chenxilinsidney
* @version 1.0
* @date 2015-01-19
*/
#include "sequence_list_dynamic.h"
/**
* @brief initialize the list.
*
* @param[in,out] L list struct pointer
*
*/
void InitList(SqList* L)
{
assert(L != NULL);
/// initialize length list size and malloc memory
if ((L->data = malloc(LIST_INIT_SIZE * sizeof(ElementType))) == NULL) {
assert(0);
exit(EXIT_FAILURE);
}
L->length = 0;
L->listsize = LIST_INIT_SIZE;
}
/**
* @brief destroy the list.
*
* @param[in,out] L list struct pointer
*
*/
void DestroyList(SqList* L)
{
assert(L != NULL && L->length >= 0 && L->length <= L->listsize);
/// clear length list size and free memory
free(L->data);
L->data = NULL;
L->length = 0;
L->listsize = 0;
}
/**
* @brief detect if the list is empty.
*
* @param[in] L list struct pointer
*
* @return return TRUE if empty, else return FALSE
*/
Status ListEmpty(SqList* L)
{
assert(L != NULL && L->length >= 0 && L->length <= L->listsize);
/// always have length >= 0
if (L->length)
return FALSE;
else
return TRUE;
}
/**
* @brief clear the list.
*
* @param[in,out] L list struct pointer
*
*/
void ClearList(SqList* L)
{
assert(L != NULL);
/// set length only, ignore the list data
L->length = 0;
}
/**
* @brief get list length.
*
* @param[in] L list struct pointer
*
* @return list length
*/
CommonType ListLength(SqList* L)
{
assert(L != NULL && L->length >= 0 && L->length <= L->listsize);
return L->length;
}
/**
* @brief get element from the list.
*
* @param[in] L list struct pointer
* @param[in] index the index from the list
* @param[out] e the element by index
*
* @warning index begin from 1
*
* @return return OK if success, else return ERROR
*/
Status GetElem(SqList* L, CommonType index, ElementType* e)
{
assert(L != NULL && e != NULL && L->length >= 0 &&
L->length <= L->listsize);
/// index should be in reasonable range
if (index > L->length || index < 1)
return ERROR;
/// get element from list
*e = L->data[index - 1];
return OK;
}
/**
* @brief locate element by index.
*
* @param[in] L list struct pointer
* @param[in] e the element to be located
*
* @warning index begin from 1
*
* @return return the index of the element if success, else return 0
*/
CommonType LocateElem(SqList* L, ElementType e)
{
assert(L != NULL && L->length >= 0 && L->length <= L->listsize);
CommonType i;
for (i = 1; i <= L->length; i++)
if (L->data[i - 1] == e)
/// get index of the first found element from list
return i;
return 0;
}
/**
* @brief insert element to the list at given index.
*
* @param[in,out] L list struct pointer
* @param[in] index the index from the list
* @param[in] e the element to be insert
*
* @warning index begin from 1
*
* @return return OK if success, else return ERROR
*/
Status ListInsert(SqList* L, CommonType index, ElementType e)
{
assert(L != NULL && L->length >= 0 && L->length <= L->listsize);
/// list length and index should be in reasonable range
if (index > (L->length + 1) || index < 1)
return ERROR;
/// malloc memory if not enough
if (L->length == L->listsize) {
ElementType* newbase = (ElementType*)realloc(
L->data, (L->listsize + LIST_INCREMENT) * sizeof(ElementType));
if (newbase == NULL) {
assert(0);
exit(EXIT_FAILURE);
}
L->data = newbase;
L->listsize += LIST_INCREMENT;
}
/// move the element after the index position to next position
CommonType i;
for (i = L->length - 1; i >= index - 1; i--)
L->data[i + 1] = L->data[i];
/// increase list length
L->length++;
/// insert element
L->data[index - 1] = e;
return OK;
}
/**
* @brief delete element from the list.
*
* @param[in,out] L list struct pointer
* @param[in] index the index from the list
* @param[out] e the element to be deleted
*
* @warning index begin from 1
*
* @return return OK and set e if success, else return ERROR
*/
Status ListDelete(SqList* L, CommonType index, ElementType* e)
{
assert(L != NULL && e != NULL && L->length >= 0 &&
L->length <= L->listsize);
/// index should be in reasonable range
if (index > L->length || index < 1)
return ERROR;
/// get deleted element
*e = L->data[index - 1];
/// move the element after the index position to previous position
CommonType i;
for (i = index; i < L->length; i++)
L->data[i - 1] = L->data[i];
/// decrease list length
L->length--;
return OK;
}
动态单链表(linked_list_dynamic.h
linked_list_dynamic.c)：
/**
* @file linked_list_dynamic.h
* @brief dynamic linked list header.
* the data was not in the first node.
* @author chenxilinsidney
* @version 1.0
* @date 2015-01-19
*/
#ifndef __LINKED_LIST_DYNAMIC_H__
#define __LINKED_LIST_DYNAMIC_H__
#include "list.h"
/// node structure
typedef struct Node
{
ElementType data; ///< data in the node
struct Node* next; ///< pointer to next node
}Node;
/// define single linked list
typedef Node* LinkList;
/// dynamic linked list method
/// initialize list
void InitList(LinkList* L, CommonType size);
/// destroy list
void DestroyList(LinkList* L);
/// detect if list is empty
Status ListEmpty(LinkList* L);
/// clear list
void ClearList(LinkList* L);
/// get list length
CommonType ListLength(LinkList* L);
/// get element from the list
Status GetElem(LinkList* L, CommonType index, ElementType* e);
/// locate element of the index
CommonType LocateElem(LinkList* L, ElementType e);
/// insert element to the list
Status ListInsert(LinkList* L, CommonType index, ElementType e);
/// delete element from the list
Status ListDelete(LinkList* L, CommonType index, ElementType* e);
#endif // __LINKED_LIST_DYNAMIC_H__
/**
* @file linked_list_dynamic.c
* @brief dynamic linked list method implements.
* The methods use <assert.h> to help debug the program.
* @author chenxilinsidney
* @version 1.0
* @date 2015-01-19
*/
#include "linked_list_dynamic.h"
/**
* @brief initialize the list.insert node in the head of list.
* The method can be alse modified to insert node in the tail
* of list.
*
* @param[in,out] L list struct pointer
* @param[in] size list data size
*
*/
void InitList(LinkList* L, CommonType size)
{
assert(size >= 0);
/// initialize first node
if ((*L = (LinkList)malloc(sizeof(Node))) == NULL) {
assert(0);
exit(EXIT_FAILURE);
}
(*L)->next = NULL;
/// initialize other node
LinkList new_node;
while (size--) {
/// add new node to the head of the list
if ((new_node = (LinkList)malloc(sizeof(Node))) == NULL) {
assert(0);
exit(EXIT_FAILURE);
}
new_node->data = 0;
new_node->next = (*L)->next;
(*L)->next = new_node;
}
}
/**
* @brief destroy the list.
*
* @param[in,out] L list struct pointer
*
*/
void DestroyList(LinkList* L)
{
assert(L != NULL);
/// pointer to the first node
LinkList q, p = (*L);
/// free memory
while (p) {
q = p->next;
free(p);
p = q;
}
/// set first node to null
*L = NULL;
}
/**
* @brief detect if the list is empty.
*
* @param[in] L list struct pointer
*
* @return return TRUE if empty, else return FALSE
*/
Status ListEmpty(LinkList* L)
{
assert(L != NULL);
/// check the first data node
if ((*L)->next)
return FALSE;
else
return TRUE;
}
/**
* @brief clear the list.
*
* @param[in,out] L list struct pointer
*
*/
void ClearList(LinkList* L)
{
assert(L != NULL);
/// pointer to the first data node
LinkList q, p = (*L)->next;
/// free memory
while (p) {
q = p->next;
free(p);
p = q;
}
/// set first data node to NULL
(*L)->next = NULL;
}
/**
* @brief get list length.
*
* @param[in] L list struct pointer
*
* @return list length
*/
CommonType ListLength(LinkList* L)
{
assert(L != NULL);
/// pointer to the first data node
CommonType length = 0;
LinkList p = (*L)->next;
/// pointer to next node
while (p) {
p = p->next;
length++;
}
return length;
}
/**
* @brief get element from the list.
*
* @param[in] L list struct pointer
* @param[in] index the index from the list
* @param[out] e the element by index
*
* @warning index begin from 1
*
* @return return OK if success, else return ERROR
*/
Status GetElem(LinkList* L, CommonType index, ElementType* e)
{
assert(L != NULL && e != NULL);
/// pointer to the first data node
CommonType j = 1;
LinkList p = (*L)->next;
/// pointer to node of index
while (p && j < index) {
/// pointer to next node
p = p->next;
j++;
}
/// can not get the element by index
if(!p || j > index)
return ERROR;
/// get element from list
*e = p->data;
return OK;
}
/**
* @brief locate element by index.
*
* @param[in] L list struct pointer
* @param[in] e the element to be located
*
* @warning index begin from 1
*
* @return return the index of the element if success, else return 0
*/
CommonType LocateElem(LinkList* L, ElementType e)
{
assert(L != NULL);
/// pointer to the first data node
CommonType index = 0;
LinkList p = (*L)->next;
/// pointer to next node
while (p) {
index++;
/// get index of the first found element from list
if(p->data == e)
return index;
p = p->next;
}
return 0;
}
/**
* @brief insert element to the list at given index.
*
* @param[in,out] L list struct pointer
* @param[in] index the index from the list
* @param[in] e the element to be insert
*
* @warning index begin from 1
*
* @return return OK if success, else return ERROR
*/
Status ListInsert(LinkList* L, CommonType index, ElementType e)
{
assert(L != NULL);
CommonType j = 1;
/// pointer to the first node
LinkList s, p = *L;
/// pointer to node of index
while (p->next && j < index) {
p = p->next;
j++;
}
/// can not get the location by index
if(!p->next || j > index)
return ERROR;
/// malloc memory
if ((s = (LinkList)malloc(sizeof(Node))) == NULL) {
assert(0);
exit(EXIT_FAILURE);
}
/// insert element
s->data = e;
s->next = p->next;
p->next = s;
return OK;
}
/**
* @brief delete element from the list.
*
* @param[in,out] L list struct pointer
* @param[in] index the index from the list
* @param[out] e the element to be deleted
*
* @warning index begin from 1
*
* @return return OK and set e if success, else return ERROR
*/
Status ListDelete(LinkList* L, CommonType index, ElementType* e)
{
assert(L != NULL && e != NULL);
CommonType j = 1;
/// pointer to the first node
LinkList q, p = *L;
/// pointer to node of index
while (p->next && j < index) {
p = p->next;
j++;
}
/// can not get the location by index
if (!(p->next) || j > index)
return ERROR;
/// get deleted element
q = p->next;
p->next = q->next;
*e = q->data;
free(q);
return OK;
}
单链表一些知识补充：
头结点：链表的第一个有效结点前面的结点，头结点并不存放有效数据，也就是数据域为空，加头结点的主要目的是为了方便链表的操作。
首节点：链表的第一个有效结点，结点包含数据域和指针域。
尾结点：尾结点的指针域为空。
头指针：指向头结点的指针变量，它存放了头结点的地址(在这里注意一下，指针变量存放的是地址，也就是说头指针存放的是头结点的地址,一般通过头指针对链表进行操作)。