双向循环链表
一、概念
双向循环链表是指每个结点由三部分组成：数据域、直接前驱结点指针、直接后继结点指针，该链表的最后一个结点的直接后继指针指向头结点，头结点的直接前驱指针指向尾节点。
二、图解
结点图示
双向循环链表图示
三、实现源码
常量定义
typedef int ET;
双向循环链表定义
typedef struct Node
{
ET data;
Node* next;
Node* prev;
}Node;
typedef Node* BCList;
获取一个新节点
Node* CreateNode(ET val){
Node* s = (Node*)malloc(sizeof(Node));
assert(s != NULL);
s->data = val;
s->next = s->prev = s;
return s;
}
初始化一个带头结点的双向循环链表
void BCLinkedListInitial(BCList* phead){
*phead = CreateNode(-1);
}
头插法
void BCLinkedListAddFromHead(BCList* phead, ET val){
assert(phead != NULL);
Node* s = CreateNode(val);
Node* p = (*phead)->next;
s->next = p;
s->prev = *phead;
(*phead)->next = s;
p->prev = s;
}
尾插法
void BCLinkedListAddFromBack(BCList* phead, ET val){
assert(phead != NULL);
Node* s = CreateNode(val);
Node* p = (*phead)->prev;
(*phead)->prev = s;
s->next = *phead;
s->prev = p;
p->next = s;
}
显示数据
void BCLinkedListShowData(BCList phead){
Node* p = phead->next;
while (p != phead){
printf("%d ", p->data);
p = p->next;
}
printf("\n");
}
判断表是否为空
bool IsEmpty(BCList* phead){
if ((*phead)->prev == (*phead)){
return true;
}
return false;
}
删除尾部结点
void BCLinkedListDeleteFromBack(BCList* phead){
assert(phead != NULL);
if (IsEmpty(phead)){
printf("表空，无法删除！\n");
return;
}
Node* s = (*phead)->prev;
(*phead)->prev = s->prev;
s->prev->next = *phead;
free(s);
}
删除首元结点
void BCLinkedListDeleteFromHead(BCList* phead){
assert(phead != NULL);
if (IsEmpty(phead)){
printf("表空，无法删除！\n");
return;
}
Node* s = (*phead)->next;
Node* p = s->next;
(*phead)->next = p;
p->prev = *phead;
free(s);
}
获取尾结点
Node* BCLinkedListGetBack(BCList* phead){
assert(phead != NULL);
if (IsEmpty(phead)){
printf("表空，无法获得！\n");
return NULL;
}
return (*phead)->prev;
}
获取首元结点
Node* BCLinkedListGetHead(BCList* phead){
assert(phead != NULL);
if (IsEmpty(phead)){
printf("表空，无法获得！\n");
return NULL;
}
return (*phead)->next;
}
获取表长度
size_t BCLinkedListGetListLength(BCList* phead){
assert(phead != NULL);
Node* p = (*phead)->next;
size_t len = 0;
while (p != (*phead)){
p = p->next;
len++;
}
return len;
}
清空表中数据
void BCLinkedListClear(BCList* phead){
assert(phead != NULL);
Node* p = (*phead)->next;
Node* q = (*phead)->next;
while (q != (*phead)){
q = q->next;
free(p);
p = q;
}
(*phead)->next = *phead;
(*phead)->prev = *phead;
}
摧毁表结构
void BCLinkedListDestroy(BCList* phead){
assert(phead != NULL);
Node* p = (*phead)->next;
Node* q = (*phead)->next;
(*phead)->next = NULL;
while (q != NULL){
q = q->next;
free(p);
p = q;
}
*phead = NULL;
}
按值查找
Node* BCLinkedListFindByValue(BCList* phead, ET key){
assert(phead != NULL);
Node* p = (*phead)->next;
while (p != (*phead) && p->data != key){
p = p->next;
}
if (p == *phead) return NULL;
return p;
}
按值的大小插入
void BCLinkedListInsertByValue(BCList* phead, ET val){
assert(phead != NULL);
Node *p = (*phead)->next;
while (p != *phead && p->data < val){
p = p->next;
}
if (p == *phead){
BCLinkedListAddFromBack(phead, val);
}
else{
Node* s = CreateNode(val);
Node* q = p->prev;
q->next = s;
s->next = p;
p->prev = s;
s->prev = q;
}
}
将表中结点按照数据升序链接
void BCLinkedListSortByData(BCList* phead){
assert(phead != NULL);
Node *p = (*phead)->next->next;
Node *q = (*phead)->next->next;
(*phead)->prev->next = NULL;
(*phead)->next->next = (*phead);
(*phead)->prev = (*phead)->next;
while (q != NULL){
q = q->next;
if ((*phead)->next->data > p->data){
BCLinkedListAddFromHead(phead, p->data);
free(p);
}
else{
Node* temp = (*phead)->next;
while (temp->next != (*phead) && temp->data < p->data){
temp = temp->next;
}
if (temp->next == (*phead)){
BCLinkedListAddFromBack(phead, p->data);
free(p);
}
else{
p->next = temp;
p->prev = temp->prev;
temp->prev->next = p;
temp->prev = p;
}
}
p = q;
}
}
反转链表
void BCLinkedListReverseList(BCList* phead){
assert(phead != NULL);
if (IsEmpty(phead)) return;
Node* p = (*phead)->prev;
Node* q = (*phead)->prev;
(*phead)->next->prev = NULL; //创造循环结束条件
//将头结点置空
(*phead)->next = (*phead)->prev = *phead;
while (q != NULL){
q = q->prev;
BCLinkedListAddFromBack(phead, p->data);
free(p);
p = q;
}
}