1.双向链表的结构

2.双向链表的实现

首先在VS里面的源文件建立test.c和List.c,在头文件里面建立List.h

List.h:

#pragma once
#include 
#include 
#include 
typedef int LTDateType;
typedef struct ListNode
{LTDateType data;struct ListNode* next;struct ListNode* prev;
}LTNode;

2.1 初始化

List.h:

LTNode* ListInit(LTNode* phead);//初始化

List.c:

#include "List.h"
LTNode* ListInit()
{//哨兵位头结点LTNode* phead = (LTNode*)malloc(sizeof(LTNode));phead->next = phead;phead->prev = phead;return phead;
}

test.c

#include "List.h"
void TestList1()
{LTNode* plist = ListInit();
}
int main()
{TestList1();return 0;
}

2.2 打印

List.h:

void ListPrint(LTNode* phead);//打印

List.c:

void ListPrint(LTNode* phead)
{assert(phead);LTNode* cur = phead->next;while (cur != phead){printf("%d ", cur->data);cur = cur->next;}printf("\n");
}

2.3 申请结点

List.h:

LTNode* BuyListNode(LTDateType x);//申请结点 

List.c:

LTNode* BuyListNode(LTDateType x)
{LTNode* newnode = (LTNode*)malloc(sizeof(LTNode));newnode->data = x;newnode->next = NULL;newnode->prev = NULL;return newnode;
}

2.4 尾插

List.h:

void ListPushBack(LTNode* phead, LTDateType x);//尾插 

List.c:

void ListPushBack(LTNode* phead, LTDateType x)
{assert(phead);LTNode* tail = phead->prev;LTNode* newnode = BuyListNode(x);tail->next = newnode;newnode->prev = tail;phead->prev = newnode;newnode->next = phead;
}

test.c

#include "List.h"
void TestList1()
{LTNode* plist = ListInit();ListPushBack(plist, 1);ListPushBack(plist, 2);ListPushBack(plist, 3);ListPrint(plist);
}
int main()
{TestList1();return 0;
}

运行结果：

2.5 尾删

List.h:

void ListPopBack(LTNode* phead);//尾删

List.c:

void ListPopBack(LTNode* phead)
{assert(phead);assert(phead->next != phead);//排除为空的情况LTNode* tail = phead->prev;phead->prev = tail->prev;tail->prev->next = phead;free(tail);
}

test.c

#include "List.h"
void TestList1()
{LTNode* plist = ListInit();ListPushBack(plist, 1);ListPushBack(plist, 2);ListPushBack(plist, 3);ListPrint(plist);ListPopBack(plist);ListPrint(plist);}
int main()
{TestList1();return 0;
}

运行结果：

2.6 头插

List.h:

void ListPushFront(LTNode* phead, LTDateType x);//头插

List.c:

void ListPushFront(LTNode* phead, LTDateType x)
{assert(phead);LTNode* newnode = BuyListNode(x);LTNode* next = phead->next;phead->next = newnode;newnode->prev = phead;newnode->next = next;next->prev = newnode;
}

test.c

#include "List.h"
void TestList1()
{LTNode* plist = ListInit();ListPushBack(plist, 1);ListPushBack(plist, 2);ListPushBack(plist, 3);ListPrint(plist);ListPopBack(plist);ListPrint(plist);ListPushFront(plist, 10);ListPrint(plist);}
int main()
{TestList1();return 0;
}

运行结果：

2.7 头删

List.h:

void ListPopFront(LTNode* phead);//头删

List.c:

void ListPopFront(LTNode* phead)
{assert(phead);assert(phead->next != phead);LTNode* next = phead->next;LTNode* nextNext = next->next;phead->next = nextNext;nextNext->prev = phead;free(next);
}

test.c

#include "List.h"
void TestList1()
{LTNode* plist = ListInit();ListPushBack(plist, 1);ListPushBack(plist, 2);ListPushBack(plist, 3);ListPrint(plist);ListPopBack(plist);ListPrint(plist);ListPushFront(plist, 10);ListPrint(plist);ListPopFront(plist);ListPrint(plist);
}
int main()
{TestList1();return 0;
}

运行结果：

2.8 查找

List.h:

LTNode* ListFind(LTNode* phead, LTDateType x);//查找

List.c:

LTNode* ListFind(LTNode* phead, LTDateType x)
{assert(phead);LTNode* cur = phead->next;while (cur != phead){if (cur->data == x)return cur;cur = cur->next;}return NULL;
}

2.9 前插

List.h:

void ListInsert(LTNode* pos, LTDateType x);//前插

List.c:

void ListInsert(LTNode* pos, LTDateType x)
{assert(pos);LTNode* posPrev = pos->prev;LTNode* newnode = BuyListNode(x);posPrev->next = newnode;newnode->prev = posPrev;newnode->next = pos;pos->prev = newnode;
}

test.c

#include "List.h"
void TestList1()
{LTNode* plist = ListInit();ListPushBack(plist, 1);ListPushBack(plist, 2);ListPushBack(plist, 3);ListPrint(plist);ListPopBack(plist);ListPrint(plist);ListPushFront(plist, 10);ListPrint(plist);ListPopFront(plist);ListPrint(plist);LTNode* list = ListFind(plist, 2);ListInsert(plist->next->next, 20);ListPrint(plist);
}
int main()
{TestList1();return 0;
}

运行结果：

2.10 删除

List.h:

void ListErase(LTNode* pos);//删除

List.c:

void ListErase(LTNode* pos)
{assert(pos);LTNode* posPrev = pos->prev;LTNode* posNext = pos->next;posPrev->next = posNext;posNext->prev = posPrev;free(pos);pos = NULL;
}

test.c

#include "List.h"
void TestList1()
{LTNode* plist = ListInit();ListPushBack(plist, 1);ListPushBack(plist, 2);ListPushBack(plist, 3);ListPrint(plist);ListPopBack(plist);ListPrint(plist);ListPushFront(plist, 10);ListPrint(plist);ListPopFront(plist);ListPrint(plist);LTNode* list = ListFind(plist, 2);ListInsert(plist->next->next, 20);ListPrint(plist);ListErase(plist->next->next);ListPrint(plist);
}
int main()
{TestList1();return 0;
}

运行结果：

2.11 销毁

List.h:

void ListDestroy(LTNode* phead);//销毁

List.c:

void ListDestroy(LTNode* phead)
{assert(phead);LTNode* cur = phead->next;while (cur != phead);{LTNode* next = cur->next;free(cur);cur = next;}free(phead);//置空放在test.c里面，因为形参是实参的临时拷贝
}

3.完整代码展示

List.h:

#pragma once
#include 
#include 
#include 
typedef int LTDateType;
typedef struct ListNode
{LTDateType data;struct ListNode* next;struct ListNode* prev;
}LTNode;
LTNode* ListInit();//初始化
void ListPrint(LTNode* phead);//打印
LTNode* BuyListNode(LTDateType x);//申请结点 
void ListPushBack(LTNode* phead, LTDateType x);//尾插 
void ListPopBack(LTNode* phead);//尾删
void ListPushFront(LTNode* phead, LTDateType x);//头插
void ListPopFront(LTNode* phead);//头删
LTNode* ListFind(LTNode* phead, LTDateType x);//查找
void ListInsert(LTNode* pos, LTDateType x);//前插
void ListErase(LTNode* pos);//删除
void ListDestroy(LTNode* phead);//销毁

List.c:

#include "List.h"
LTNode* ListInit()
{//哨兵位头结点LTNode* phead = (LTNode*)malloc(sizeof(LTNode));phead->next = phead;phead->prev = phead;return phead;
}void ListPrint(LTNode* phead)
{assert(phead);LTNode* cur = phead->next;while (cur != phead){printf("%d ", cur->data);cur = cur->next;}printf("\n");
}LTNode* BuyListNode(LTDateType x)
{LTNode* newnode = (LTNode*)malloc(sizeof(LTNode));newnode->data = x;newnode->next = NULL;newnode->prev = NULL;return newnode;
}void ListPushBack(LTNode* phead, LTDateType x)
{assert(phead);LTNode* tail = phead->prev;LTNode* newnode = BuyListNode(x);tail->next = newnode;newnode->prev = tail;phead->prev = newnode;newnode->next = phead;
}void ListPopBack(LTNode* phead)
{assert(phead);assert(phead->next != phead);//排除为空的情况LTNode* tail = phead->prev;phead->prev = tail->prev;tail->prev->next = phead;free(tail);
}void ListPushFront(LTNode* phead, LTDateType x)
{assert(phead);LTNode* newnode = BuyListNode(x);LTNode* next = phead->next;phead->next = newnode;newnode->prev = phead;newnode->next = next;next->prev = newnode;
}void ListPopFront(LTNode* phead)
{assert(phead);assert(phead->next != phead);LTNode* next = phead->next;LTNode* nextNext = next->next;phead->next = nextNext;nextNext->prev = phead;free(next);
}LTNode* ListFind(LTNode* phead, LTDateType x)
{assert(phead);LTNode* cur = phead->next;while (cur != phead){if (cur->data == x)return cur;cur = cur->next;}return NULL;
}void ListInsert(LTNode* pos, LTDateType x)
{assert(pos);LTNode* posPrev = pos->prev;LTNode* newnode = BuyListNode(x);posPrev->next = newnode;newnode->prev = posPrev;newnode->next = pos;pos->prev = newnode;
}void ListErase(LTNode* pos)
{assert(pos);LTNode* posPrev = pos->prev;LTNode* posNext = pos->next;posPrev->next = posNext;posNext->prev = posPrev;free(pos);pos = NULL;
}void ListDestroy(LTNode* phead)
{assert(phead);LTNode* cur = phead->next;while (cur != phead);{LTNode* next = cur->next;free(cur);cur = next;}free(phead);//置空放在test.c里面，因为形参是实参的临时拷贝
}

test.c

#include "List.h"
void TestList1()
{LTNode* plist = ListInit();ListPushBack(plist, 1);ListPushBack(plist, 2);ListPushBack(plist, 3);ListPrint(plist);ListPopBack(plist);ListPrint(plist);ListPushFront(plist, 10);ListPrint(plist);ListPopFront(plist);ListPrint(plist);LTNode* list = ListFind(plist, 2);ListInsert(plist->next->next, 20);ListPrint(plist);ListErase(plist->next->next);ListPrint(plist);
}
int main()
{TestList1();return 0;
}

4.顺序表和链表的区别

备注：缓存利用率参考存储体系结构以及局部原理性。

5.链表OJ题

5.1 环形链表（1）

给你一个链表的头节点 head ，判断链表中是否有环。如果链表中有某个节点，可以通过连续跟踪 next 指针再次到达，则链表中存在环。 为了表示给定链表中的环，评测系统内部使用整数 pos 来表示链表尾连接到链表中的位置（索引从 0 开始）。注意：pos 不作为参数进行传递 。仅仅是为了标识链表的实际情况。如果链表中存在环 ，则返回 true 。 否则，返回 false 。

链接：https://leetcode.cn/problems/linked-list-cycle/

bool hasCycle(struct ListNode *head) {struct ListNode* slow=head,*fast=head;while(fast&&fast->next){slow=slow->next;fast=fast->next->next;if(slow==fast){return true;}}return false;
}

5.2 环形链表（2）

给定一个链表的头节点 head ，返回链表开始入环的第一个节点。 如果链表无环，则返回 null。如果链表中有某个节点，可以通过连续跟踪 next 指针再次到达，则链表中存在环。 为了表示给定链表中的环，评测系统内部使用整数 pos 来表示链表尾连接到链表中的位置（索引从 0 开始）。如果 pos 是 -1，则在该链表中没有环。注意：pos 不作为参数进行传递，仅仅是为了标识链表的实际情况。不允许修改链表。

链接：https://leetcode.cn/problems/linked-list-cycle-ii/description/

struct ListNode *detectCycle(struct ListNode *head) {struct ListNode* slow=head,*fast=head;while(fast&&fast->next){slow=slow->next;fast=fast->next->next;if(slow==fast){//相遇struct ListNode* meet=slow;//公式while(meet!=head){meet=meet->next;head=head->next;}return meet;}}return NULL;
}

5.3 复杂链表的复制

给你一个长度为 n 的链表，每个节点包含一个额外增加的随机指针 random ，该指针可以指向链表中的任何节点或空节点。
构造这个链表的 深拷贝。 深拷贝应该正好由 n 个 全新 节点组成，其中每个新节点的值都设为其对应的原节点的值。新节点的 next 指针和 random 指针也都应指向复制链表中的新节点，并使原链表和复制链表中的这些指针能够表示相同的链表状态。复制链表中的指针都不应指向原链表中的节点 。
例如，如果原链表中有 X 和 Y 两个节点，其中 X.random --> Y 。那么在复制链表中对应的两个节点 x 和 y ，同样有 x.random --> y 。返回复制链表的头节点。用一个由 n 个节点组成的链表来表示输入/输出中的链表。
每个节点用一个 [val, random_index] 表示：
val：一个表示 Node.val 的整数。
random_index：随机指针指向的节点索引（范围从 0 到 n-1）；如果不指向任何节点，则为 null 。
你的代码 只 接受原链表的头节点 head 作为传入参数。

链接：https://leetcode.cn/problems/copy-list-with-random-pointer/description/

struct Node* copyRandomList(struct Node* head) {//1.拷贝结点插入原结点的后面struct Node* cur=head;while(cur){struct Node* copy=(struct Node*)malloc(sizeof(struct Node));copy->val=cur->val;//插入copy结点copy->next=cur->next;cur->next=copy;cur=copy->next;}//2.根据原结点，处理copy结点的randomcur=head;while(cur){struct Node* copy=cur->next;if(cur->random==NULL){copy->random=NULL;}else{copy->random=cur->random->next;}cur=copy->next;}struct Node* copyHead=NULL,*copyTail=NULL;cur=head;while(cur){struct Node* copy=cur->next;struct Node* next=copy->next;if(copyTail==NULL){copyHead=copyTail=copy;}else{copyTail->next=copy;copyTail=copy;}cur->next=next;cur=next;}return copyHead;
}