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前言

各位小伙伴大家好！上期小编给大家讲解了数据结构中的顺序表应用，接下来讲讲数据结构中的双向链表！

1. 初步认识双向链表

1.1 定义

双向链表也叫双链表，是链表的一种，它的每个数据结点中都有两个指针，分别指向直接后继和直接前驱。

1.2 结构

1.3 储存

//双链表节点结构体
typedef struct DoubleLinkNode
{char data;struct DoubleLinkNode* prior;struct DoubleLinkNode* next;
} Node,*NodePtr;

2. 双向链表的方法（接口函数）

2.1 动态申请空间

【本质】动态开辟一块sizeof(ListNode)大小的空间进行存储

// 动态申请一个结点
ListNode *BuyListNode(LTDateType x) {ListNode *node = (ListNode *) malloc(sizeof(ListNode));node->data = x;node->prev = NULL;node->next = NULL;return node;
}

2.2 创建哨兵位

// 创建返回链表的哨兵位
ListNode *ListInit() {ListNode *pHead = BuyListNode(-1);pHead->prev = pHead;pHead->next = pHead;return pHead;
}

2.3 查找指定数据

// 双向链表查找
ListNode *ListFind(ListNode *pHead, LTDateType x) {assert(pHead);ListNode *curr = pHead->next;while (curr != pHead) {if (curr->data == x) {return curr;}curr = curr->next;}return NULL;
}

2.4 指定位置插入

// 双向链表在pos位置插入x
void ListInsert(ListNode *pos, LTDateType x) {assert(pos);ListNode *newNode = BuyListNode(x);ListNode *prev = pos->prev;newNode->prev = prev;newNode->next = pos;prev->next = newNode;pos->prev = newNode;
}

2.5 指定位置删除

// 双向链表在pos位置删除
void ListErase(ListNode *pos) {assert(pos);assert(pos != pos->next);pos->next->prev = pos->prev;pos->prev->next = pos->next;free(pos);
}

2.6 头部插入

// 双向链表头插
void ListPushFront(ListNode *pHead, LTDateType x) {ListInsert(pHead->next, x);
}

2.7 头部删除

// 双向链表头删
void ListPopFront(ListNode *pHead) {ListErase(pHead->next);
}

2.8 尾部插入

// 双向链表尾插
void ListPushBack(ListNode *pHead, LTDateType x) {ListInsert(pHead, x);
}

2.9 尾部删除

// 双向链表尾删
void ListPopBack(ListNode *pHead) {ListErase(pHead->prev);
}

2.10 计算链表大小

// 计算大小
int ListSize(ListNode *pHead) {ListNode *curr = pHead->next;int size = 0;while (curr != pHead) {size++;curr = curr->next;}return size;
}

2.11 销毁链表

// 销毁(手动置空)
void ListDestory(ListNode *pHead) {ListNode *curr = pHead->next;while (curr != pHead) {ListNode *next = curr->next;free(curr);curr = next;}free(pHead);
}

3. 双向链表的代码实现

#include <stdio.h>
#include <stdlib.h>
int Linklength;//双链表节点结构体
typedef struct DoubleLinkNode
{char data;struct DoubleLinkNode* prior;struct DoubleLinkNode* next;
} Node,*NodePtr;//初始化
NodePtr initLinkList()
{NodePtr LinkHeader = (NodePtr)malloc(sizeof(Node));LinkHeader->data = '\0';LinkHeader->next = NULL;LinkHeader->prior = NULL;Linklength = 0;return LinkHeader;
}//寻找尾节点
NodePtr tailNodeSearch(NodePtr LinkHeader)
{NodePtr p = LinkHeader;while(p->next){p = p->next;}return p;
}//正向打印
void printListByHead(NodePtr LinkHeader)
{NodePtr p = LinkHeader->next;while (p){printf("%c",p->data);p = p->next;}printf("\n");
}//反向打印
void printListByTail(NodePtr LinkHeader)
{NodePtr tail = tailNodeSearch(LinkHeader);NodePtr p = tail;while (p){printf("%c",p->data);p = p->prior;}printf("\n");
}//在某位置插入
void ListInsert(NodePtr LinkHeader, int InsertPosition, char InsertChar)
{if(InsertPosition < 0 || InsertPosition > Linklength){printf("The position %d out of range of linked list!\n",InsertPosition);return ;}NodePtr p,q,r,tail;p = LinkHeader;for(int i = 0; i < InsertPosition; ++i){p = p->next;if(!p){printf("The position %d out of range of linked list!\n",InsertPosition);return ;}}q = (NodePtr)malloc(sizeof(Node));q->data = InsertChar;r = p->next;q->prior = p;q->next = r;p->next = q;if(r){r->prior = q;}Linklength++;
}//删除第一个数据域为x的节点
void ListDeleteByData(NodePtr LinkHeader, char DeleteChar)
{NodePtr p,q,r;p = LinkHeader;while(p->next && p->next->data != DeleteChar){p = p->next;}if(!(p->next)){printf("The char '%c' does't exist.\n",DeleteChar);return ;}q = p->next;r = q->next;p->next = r;if(r){r->prior = p;}free(q);Linklength--;
}//删除第Position个节点
void ListDeleteByPosition(NodePtr LinkHeader, int Position)
{NodePtr p,q,r,tail;int j = 0;tail = tailNodeSearch(LinkHeader);p = LinkHeader;while(p->next && j < Position){p = p->next;++j;}if(!(p->next) || j > Position){printf("Can't delete it!\n");return ;}q = p->next;r = q->next;p->next = r;if(r){r->prior = p;}free(q);Linklength--;
}//链表节点的读取（打印链表中第position个数据元素的值）
void GetElement(NodePtr LinkHeader, int position)
{NodePtr p,q,r;if(position <= Linklength/2){p = LinkHeader->next;int j = 0;while(p && j < position){p = p->next;++j;}if(!p || j > position){printf("Can't get it !\n");return ;}printf("The element at its %d-th position is %c\n",position,p->data);}else{p = tailNodeSearch(LinkHeader);int j = 0;while(p->prior && j < Linklength-position-1){p = p->prior;++j;}if(!p || j > Linklength-position-1){printf("Can't get it !\n");return ;}printf("The element at its %d-th position is %c\n",position,p->data);}
}//测试
void insertDeleteTest()
{printf("---------------Initialize bidirectional linked list--------------\n");NodePtr tempList = initLinkList();printListByHead(tempList);printListByTail(tempList);printf("---------------Inserts a node at the specified location--------------\n");ListInsert(tempList,0,'H');ListInsert(tempList,1,'e');ListInsert(tempList,2,'l');ListInsert(tempList,3,'l');ListInsert(tempList,4,'o');printListByHead(tempList);printListByTail(tempList);printf("---------------Gets the node data field at the specified location--------------\n");GetElement(tempList,0);GetElement(tempList,4);GetElement(tempList,5);printf("---------------Delete the first node whose data field is X--------------\n");ListDeleteByData(tempList,'e');printListByHead(tempList);printListByTail(tempList);printf("---------------Delete the position node--------------\n");ListDeleteByPosition(tempList,3);printListByHead(tempList);printListByTail(tempList);
}int main()
{insertDeleteTest();
}

结语

以上就是小编对双向链表的讲解。
如果觉得小编讲的还可以，还请一键三连。互三必回！
持续更新中~！