目录
双链表的引入是因为单链表要访问某个结点的前驱结点时,只能从头开始遍历,访问后驱结点的复杂度为O(1),访问前驱结点的复杂度为O(n)。为了克服上述缺点,引入了双链表。
双链表的引进,对于链表的操作有了极大的遍历;
链表由单向的链变成了双向链。
双向链表(double linked list)是在单链表的每个结点中再设置一个指向其前驱结点的指针域。
包含了一个数据域,两个指针域(指向前后驱节点)
- // 带头+双向+循环链表增删查改实现
- typedef int LTDataType;
- typedef struct ListNode
- {
- LTDataType data; //数据
- struct ListNode* next; //下一个指针域
- struct ListNode* prev; //上一个指针域
- }ListNode;
双向链表一般都是带头节点的,在链表中,带了头节点对于链表分割这一问题有了简单化;
动态开辟出一块空间,前后指针都指向自己;
- //初始化链表头头节点
- ListNode* ListInit()
- {
- ListNode* phead = (ListNode*)malloc(sizeof(ListNode));
- assert(phead);
- phead->data = -1;
- phead->next = phead;
- phead->prev = phead;
- return phead;
- }
这里置NULL,和单链表的置NULL,是一样的意思,对后续的操作提供便利;
- // 创建返回链表的结点.
- ListNode* ListCreate(LTDataType x)
- {
- ListNode* newnode = (ListNode*)malloc(sizeof(ListNode));
- assert(newnode);
- newnode->data = x;
- newnode->next = NULL;
- newnode->prev = NULL;
- return newnode;
- }
单链表的尾插还需要考虑是否存在第一个节点,这里直接插入即可;
注意操作顺序
- // 双向链表尾插
- void ListPushBack(ListNode* phead, LTDataType x)
- {
- assert(phead);
- ListNode* newnode = ListCreate(x);
-
- struct ListNode* tail = phead->prev;
- // phead tail newnode
-
- //newnode->prev = phead->prev;
- //newnode->next = phead;
- //phead->prev->next = newnode;
- //phead->prev = newnode;
-
- //注意前后顺序
- newnode->prev = tail;
- tail->next = newnode;
- newnode->next = phead;
- phead->prev = newnode;
-
- }
这里的关键就是从哪里开始?如何判断结束(因为是循环)?
我们可以从头结点的下一个开始打印,当遇到头结点即是结束;
- // 双向链表打印
- void ListPrint(ListNode* phead)
- {
- assert(phead);
- struct ListNode* cur = phead->next;
- printf("哨兵位<=>");
- while (cur != phead)
- {
- printf("%d<=>", cur->data);
- cur = cur->next;
- }
- printf("\n");
- }
要多一个断言判断:如果只有一个头指针就不用操作了;
保存尾结点的前驱,释放尾结点即可
- // 双向链表尾删
- void ListPopBack(ListNode* phead)
- {
- assert(phead);
- assert(phead->next != phead); //只有头指针不删
-
- struct ListNode* cur = phead->prev;
- struct ListNode* curPrev = cur->prev; //尾节点的上一个
- phead->prev = curPrev;
- curPrev->next = phead;
- free(cur);
- cur = NULL;
- }
和尾插操作相似,定义头节点的下一个结点,进行链接即可;
注意顺序;
- // 双向链表头插
- void ListPushFront(ListNode* phead, LTDataType x)
- {
- assert(phead);
-
- ListNode* newnode = ListCreate(x);
- struct ListNode* cur = phead->next;
-
- newnode->next = cur;
- cur->prev = newnode;
- newnode->prev = phead;
- phead->next = newnode;
- }
删除操作一般都需要判断一下是否只有头节点。判断双向链表的条件是:phead->next != phead;
- // 双向链表头删
- void ListPopFront(ListNode* phead)
- {
- assert(phead);
- assert(phead->next != phead); //只有头指针不删
-
- ListNode* cur = phead->next;
- ListNode* next = cur->next;
-
- phead->next = next;
- next->prev = phead;
-
- free(cur);
- cur = NULL;
- }
找到该结点后,返回的是指针,而不是数据,返回该指针位置,方便后续操作
- // 双向链表查找
- ListNode* ListFind(ListNode* phead, LTDataType x)
- {
- assert(phead);
-
- ListNode* cur = phead->next;
- while (cur != phead)
- {
- if (cur->data == x)
- return cur;
- cur = cur->next;
- }
- return NULL;
- }
- // 双向链表在pos的前面进行插入
- void ListInsert(ListNode* pos, LTDataType x)
- {
- assert(pos); //检查pos位置是否有效
- ListNode* newnode = ListCreate(x);
-
- newnode->next = pos; //将newnode节点next prev 链接前后节点
- newnode->prev = pos->prev;
- pos->prev->next = newnode;
- pos->prev = newnode;
- }
- // 双向链表删除pos位置的节点
- void ListErase(ListNode* pos)
- {
- assert(pos);
-
- ListNode* posPrev = pos->prev;
- ListNode* next = pos->next;
-
- posPrev->next = next;
- next->prev = posPrev;
- free(pos);
- pos = NULL;
- }
- // 双向链表销毁
- void ListDestory(ListNode* phead)
- {
- assert(phead);
- ListNode* cur = phead->prev;
- while (cur != phead) //将除了头结点的都销毁
- {
- ListNode* curPrev = cur->prev;
- free(cur);
- cur = curPrev;
- }
- free(phead); //再释放头结点
- //phead = NULL;
- }
- #define _CRT_SECURE_NO_WARNINGS 1
- #include"List.h"
-
-
- void test1()
- {
- ListNode* plist = NULL;
- plist = ListInit();
- ListPushBack(plist, 1);
- ListPushBack(plist, 2);
- ListPushBack(plist, 3);
- ListPushBack(plist, 4);
- ListPrint(plist);
-
- ListPopBack(plist);
- ListPrint(plist);
-
- ListPopBack(plist);
- ListPrint(plist);
-
- ListPopBack(plist);
- ListPrint(plist);
-
- ListPopBack(plist);
- ListPrint(plist);
-
- }
-
-
- void test2()
- {
- ListNode* plist = NULL;
- plist = ListInit();
-
- ListPrint(plist);
- //ͷ
- ListPushFront(plist, 6);
- ListPrint(plist);
-
- //ͷɾ
- ListPopFront(plist);
- ListPrint(plist);
-
- }
-
- void test3()
- {
- ListNode* plist = NULL;
- plist = ListInit();
- ListPushBack(plist, 1);
- ListPushBack(plist, 2);
- ListPushBack(plist, 3);
- ListPushBack(plist, 4);
- ListPrint(plist);
-
- //βɾ
- ListPopBack(plist);
- ListPopBack(plist);
- ListPopBack(plist);
-
- ListNode* pos = ListFind(plist,1);
-
- ListInsert(pos, 666);
- ListPrint(plist);
-
- ListErase(pos);
- ListPrint(plist);
-
- ListDestory(plist);
- }
- int main()
- {
- //test1();
- //test2();
- test3();
- return 0;
- }
- #define _CRT_SECURE_NO_WARNINGS 1
- #include"List.h"
-
-
- //初始化链表头头节点
- ListNode* ListInit()
- {
- ListNode* phead = (ListNode*)malloc(sizeof(ListNode));
- assert(phead);
- phead->data = -1;
- phead->next = phead;
- phead->prev = phead;
- return phead;
- }
-
- // 创建返回链表的头结点.
- ListNode* ListCreate(LTDataType x)
- {
- ListNode* newnode = (ListNode*)malloc(sizeof(ListNode));
- assert(newnode);
- newnode->data = x;
- newnode->next = NULL;
- newnode->prev = NULL;
- return newnode;
- }
-
- // 双向链表尾插
- void ListPushBack(ListNode* phead, LTDataType x)
- {
- assert(phead);
- ListNode* newnode = ListCreate(x);
-
- struct ListNode* tail = phead->prev;
- // phead tail newnode
-
- //newnode->prev = phead->prev;
- //newnode->next = phead;
- //phead->prev->next = newnode;
- //phead->prev = newnode;
-
- //注意前后顺序
- newnode->prev = tail;
- tail->next = newnode;
- newnode->next = phead;
- phead->prev = newnode;
-
- }
-
- // 双向链表打印
- void ListPrint(ListNode* phead)
- {
- assert(phead);
- struct ListNode* cur = phead->next;
- printf("哨兵位<=>");
- while (cur != phead)
- {
- printf("%d<=>", cur->data);
- cur = cur->next;
- }
- printf("\n");
- }
-
- // 双向链表尾删
- void ListPopBack(ListNode* phead)
- {
- assert(phead);
- assert(phead->next != phead); //只有头指针不删
-
- struct ListNode* cur = phead->prev;
- struct ListNode* curPrev = cur->prev; //尾节点的上一个
- phead->prev = curPrev;
- curPrev->next = phead;
- free(cur);
- cur = NULL;
- }
-
- // 双向链表头插
- void ListPushFront(ListNode* phead, LTDataType x)
- {
- assert(phead);
-
- ListNode* newnode = ListCreate(x);
- struct ListNode* cur = phead->next;
-
- newnode->next = cur;
- cur->prev = newnode;
- newnode->prev = phead;
- phead->next = newnode;
- }
-
- // 双向链表头删
- void ListPopFront(ListNode* phead)
- {
- assert(phead);
- assert(phead->next != phead); //只有头指针不删
-
- ListNode* cur = phead->next;
- ListNode* next = cur->next;
-
- phead->next = next;
- next->prev = phead;
-
- free(cur);
- cur = NULL;
- }
-
- // 双向链表查找
- ListNode* ListFind(ListNode* phead, LTDataType x)
- {
- assert(phead);
-
- ListNode* cur = phead->next;
- while (cur != phead)
- {
- if (cur->data == x)
- return cur;
- cur = cur->next;
- }
- return NULL;
- }
-
- // 双向链表在pos的前面进行插入
- void ListInsert(ListNode* pos, LTDataType x)
- {
- assert(pos); //检查pos位置是否有效
- ListNode* newnode = ListCreate(x);
-
- newnode->next = pos; //将newnode节点next prev 链接前后节点
- newnode->prev = pos->prev;
- pos->prev->next = newnode;
- pos->prev = newnode;
- }
-
- // 双向链表删除pos位置的节点
- void ListErase(ListNode* pos)
- {
- assert(pos);
-
- ListNode* posPrev = pos->prev;
- ListNode* next = pos->next;
-
- posPrev->next = next;
- next->prev = posPrev;
- free(pos);
- pos = NULL;
- }
-
- // 双向链表销毁
- void ListDestory(ListNode* phead)
- {
- assert(phead);
- ListNode* cur = phead->prev;
- while (cur != phead) //将除了头节点的都销毁
- {
- ListNode* curPrev = cur->prev;
- free(cur);
- cur = curPrev;
- }
- free(phead);
- //phead = NULL;
- }
- #pragma once
- #include<stdio.h>
- #include<assert.h>
- #include<stdlib.h>
-
- // 带头+双向+循环链表增删查改实现
- typedef int LTDataType;
- typedef struct ListNode
- {
- LTDataType data; //数据
- struct ListNode* next; //下一个指针域
- struct ListNode* prev; //上一个指针域
- }ListNode;
-
- // 创建返回链表的头结点.
- ListNode* ListCreate(LTDataType x);
-
- //初始化链表头头节点
- ListNode* ListInit();
-
- // 双向链表尾插
- void ListPushBack(ListNode* pHead, LTDataType x);
-
- // 双向链表打印
- void ListPrint(ListNode* pHead);
-
- // 双向链表尾删
- void ListPopBack(ListNode* pHead);
-
- // 双向链表头插
- void ListPushFront(ListNode* pHead, LTDataType x);
-
- // 双向链表头删
- void ListPopFront(ListNode* pHead);
-
- // 双向链表查找
- ListNode* ListFind(ListNode* pHead, LTDataType x);
-
- // 双向链表在pos的前面进行插入
- void ListInsert(ListNode* pos, LTDataType x);
-
- // 双向链表删除pos位置的节点
- void ListErase(ListNode* pos);
-
- // 双向链表销毁
- void ListDestory(ListNode* pHead);
以上就是我对【数据结构|双向链表|增删改查】的介绍,不足之处,还望指点。