数据结构——单链表

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前言——什么链表

链表的概念及结构概念：
链表是一种物理存储结构上非连续、非顺序的存储结构，数据元素的逻辑顺序是通过链表中的指针链接次序实现的 。

链表形象图

链表具体表现是怎么样的呢？让我们通过下面的图片来了解一下！

形象一点形容呢，那就像一个车厢相互链接的火车，这样好记住多了吧！

注意：
. 从上图可看出，链式结构在逻辑上是连续的，但在物理上不一定连续
. 现实中的结点一般是都是从堆上申请来的
. 从堆上申请的空间，是按照一定的策略来分配的，两次申请的空间可能连续，也可能不连续

链表分类

实际中链表的结构非常多样，以下情况组合起来就有8种链表结构：

1. 单向或者双向：
   

2. 带头或者不带头：
   

3. 循环或者非循环：
   

虽然有这么多的链表的结构，但是我们实际中最常用还是两种结构：
无头单向非循环链表

带头双向循环链表

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今天我们要实现的是无头单向非循环链表，让我们跟随下面的步骤来建立单链表吧

一、Single_linked_list.h头文件的建立

1.头文件的声明

#pragma once
#include<stdio.h>
#include<stdlib.h>
#include<assert.h>

2.单链表的接口实现

typedef int SLTDataType;//类型重命名
//单链表接口定义
typedef struct SListNode
{SLTDataType data;struct SListNode* next;
}SLTNode;

3.打印函数以及创建结点函数的声明

//打印
void SLTPrint(SLTNode* phead);
//创建结点
SLTNode* BuySListNode(SLTDataType x);

4.尾插、头插函数的声明

//尾插
void SLTPushBack(SLTNode** pphead, SLTDataType x);
//头插
void SLTPushFront(SLTNode** pphead, SLTDataType x);

5.尾删头删函数的声明

//尾删
void SLTPopBack(SLTNode** pphead);
//头删
void SLTPopFront(SLTNode** pphead);

6.查找函数的声明

SLTNode* SLTFind(SLTNode* phead, SLTDataType x);

7.定点pos前后插入函数的声明

// 在pos之前插入x
void SLTInsert(SLTNode** pphead, SLTNode* pos, SLTDataType x);
// 在pos以后插入x
void SLTInsertAfter(SLTNode** pphead,SLTNode* pos, SLTDataType x);

8.定点删除pos或删除pos后一位结点的函数的声明

// 删除pos位置
void SLTErase(SLTNode** pphead, SLTNode* pos);
// 删除pos的后一个位置
void SLTEraseAfter(SLTNode** pphead, SLTNode* pos);

二、Single_linked_list.c功能函数的定义

1.头文件的声明

#include "Single_linked_list.h"

2.打印函数以及创建结点函数的定义

//打印
void SLTPrint(SLTNode* phead)
{SLTNode* cur = phead;while (cur)//cur!=NULL为真{printf("%d ", cur->data);cur = cur->next;}printf("NULL\n");//打印尾结点的next结点NULL
}//创建结点
SLTNode* BuySListNode(SLTDataType x)
{SLTNode* newnode = (SLTNode*)malloc(sizeof(SLTNode));//创建一个新结点if (newnode == NULL)//创建失败返回错误结束程序{perror("malloc fail");exit(-1);}newnode->data = x;newnode->next = NULL;//将新结点的next结点置为NULLreturn newnode;
}

3.尾插、头插函数的定义

//尾插
//传入结构体指针，用二级指针接收
void SLTPushBack(SLTNode** pphead, SLTDataType x)
{SLTNode* newnode = BuySListNode(x);//调用函数创建新结点//两种情况 头结点为空时和头结点不为空时if (*pphead == NULL){// 改变的结构体的指针，所以要用二级指针*pphead = newnode;}else{SLTNode* tail = *pphead;while (tail->next != NULL)//遍历链表到尾结点{tail = tail->next;}// 改变的结构体，用结构体的指针即可tail->next = newnode;}
}//头插
void SLTPushFront(SLTNode** pphead, SLTDataType x)
{SLTNode* newnode = BuySListNode(x);newnode->next = *pphead;// 改变的结构体的指针，所以要用二级指针*pphead = newnode;
}

4.尾删头删函数的定义

//尾删
void SLTPopBack(SLTNode** pphead)
{assert(*pphead);//判断*pphead是否为空//一个节点if ((*pphead)->next == NULL){free(*pphead);*pphead = NULL;}else//一个以上节点{SLTNode* tail = *pphead;while (tail->next->next)//遍历链表到尾结点{tail = tail->next;}free(tail->next);tail->next = NULL;}
}//头删
void SLTPopFront(SLTNode** pphead)
{assert(*pphead);//判断*pphead是否为空SLTNode* newhead = (*pphead)->next;free(*pphead);*pphead = newhead;
}

当然，尾删不只一种方法，另一种方法就是：

void SLTPopBack(SLTNode** pphead)
{assert(*pphead);if ((*pphead)->next == NULL){free(*pphead);*pphead = NULL;}else{SLTNode* tailPrev = NULL;//设置一个前驱结点，方便置空SLTNode* tail = *pphead;while (tail->next){tailPrev = tail;tail = tail->next;}free(tail);tailPrev->next = NULL;}
}

5.查找函数的定义

SLTNode* SLTFind(SLTNode* phead, SLTDataType x) {SLTNode* cur = phead;while (cur != NULL&&cur->data != x ) {cur = cur->next;}if (cur == NULL) {printf("未查找到有效结点\n");exit(-1);}return cur;
}

6.定点pos前后插入函数的定义

// 在pos之前插入x
void SLTInsert(SLTNode** pphead, SLTNode* pos, SLTDataType x) {SLTNode* newnode = BuySListNode(x);SLTNode* curPrev = *pphead;SLTNode* cur = SLTFind(curPrev,pos->data);if (curPrev == cur) {newnode->next = *pphead;*pphead = newnode;}else {while (curPrev->next != cur) {curPrev = curPrev->next;}newnode->next = cur;curPrev->next = newnode;}
}// 在pos以后插入x
void SLTInsertAfter(SLTNode** pphead,SLTNode* pos, SLTDataType x) {SLTNode* newnode = BuySListNode(x);SLTNode* temp = *pphead;SLTNode* cur = SLTFind(temp, pos->data);newnode->next = cur->next;cur->next = newnode;
}

7.定点删除pos或删除pos后一位结点的函数的定义

// 删除pos位置
void SLTErase(SLTNode** pphead, SLTNode* pos) {SLTNode* temp = *pphead;SLTNode* curPrev = *pphead;SLTNode* cur = SLTFind(temp, pos->data);if (curPrev == cur) {temp = cur->next;free(cur);cur = temp;}else {while (curPrev->next != cur) {curPrev = curPrev->next;}curPrev->next = cur->next;free(cur);cur = NULL;}
}// 删除pos的后一个位置
void SLTEraseAfter(SLTNode** pphead, SLTNode* pos) {SLTNode* temp = *pphead;SLTNode* cur = SLTFind(temp, pos->data);if (cur->next == NULL) {return;}else {temp = cur->next;cur->next = temp->next;free(temp);temp = NULL;}
}

Single_linked_list_test.c主函数的定义

1.头文件的声明

#include "Single_linked_list.h"

2.测试调用函数的定义

void TestSList() {SLTNode* plist = NULL;SLTPushBack(&plist, 1);SLTPushBack(&plist, 2);SLTPushBack(&plist, 3);SLTPushBack(&plist, 4);SLTPushBack(&plist, 5);SLTPrint(plist);SLTPushFront(&plist, 10);SLTPushFront(&plist, 20);SLTPushFront(&plist, 30);SLTPushFront(&plist, 40);SLTPrint(plist);SLTNode* pos = BuySListNode(3);SLTInsert(&plist,pos, 6);free(pos);pos = NULL;SLTPrint(plist);pos = BuySListNode(3);SLTInsertAfter(&plist, pos, 7);free(pos);pos = NULL;SLTPrint(plist);pos = BuySListNode(6);SLTErase(&plist, pos);free(pos);pos = NULL;SLTPrint(plist);pos = BuySListNode(7);SLTErase(&plist, pos);free(pos);pos = NULL;SLTPrint(plist);pos = BuySListNode(3);SLTEraseAfter(&plist, pos);free(pos);pos = NULL;SLTPrint(plist);pos = BuySListNode(3);SLTEraseAfter(&plist, pos);free(pos);pos = NULL;SLTPrint(plist);pos = BuySListNode(1);SLTEraseAfter(&plist, pos);free(pos);pos = NULL;SLTPrint(plist);
}

3.主函数的定义

int main()
{TestSList();return 0;
}

四、代码运行测试

示例一：

void TestSList2()
{SLTNode* plist = NULL;SLTPushBack(&plist, 1);SLTPushBack(&plist, 2);SLTPushBack(&plist, 3);SLTPushBack(&plist, 4);SLTPushBack(&plist, 5);SLTPrint(plist);SLTPushFront(&plist, 10);SLTPushFront(&plist, 20);SLTPushFront(&plist, 30);SLTPushFront(&plist, 40);SLTPrint(plist);
}

运行结果：

示例二：

void TestSList3()
{SLTNode* plist = NULL;SLTPushBack(&plist, 1);SLTPushBack(&plist, 2);SLTPushBack(&plist, 3);SLTPushBack(&plist, 4);SLTPushBack(&plist, 5);SLTPrint(plist);SLTPopBack(&plist);SLTPrint(plist);SLTPopBack(&plist);SLTPrint(plist);SLTPopBack(&plist);SLTPrint(plist);SLTPopBack(&plist);SLTPrint(plist);SLTPopBack(&plist);SLTPrint(plist);}

运行结果：

示例三：

void TestSList5() {SLTNode* plist = NULL;SLTPushBack(&plist, 1);SLTPushBack(&plist, 2);SLTPushBack(&plist, 3);SLTPushBack(&plist, 4);SLTPushBack(&plist, 5);SLTPrint(plist);SLTNode* pos = BuySListNode(3);SLTInsert(&plist,pos, 6);free(pos);pos = NULL;SLTPrint(plist);pos = BuySListNode(3);SLTInsertAfter(&plist, pos, 7);free(pos);pos = NULL;SLTPrint(plist);pos = BuySListNode(6);SLTErase(&plist, pos);free(pos);pos = NULL;SLTPrint(plist);pos = BuySListNode(7);SLTErase(&plist, pos);free(pos);pos = NULL;SLTPrint(plist);pos = BuySListNode(3);SLTEraseAfter(&plist, pos);free(pos);pos = NULL;SLTPrint(plist);pos = BuySListNode(3);SLTEraseAfter(&plist, pos);free(pos);pos = NULL;SLTPrint(plist);pos = BuySListNode(1);SLTEraseAfter(&plist, pos);free(pos);pos = NULL;SLTPrint(plist);
}

运行结果：

五、Single_linked_list完整代码演示：

Single_linked_list.h

#pragma once
#include<stdio.h>
#include<stdlib.h>
#include<assert.h>typedef int SLTDataType;//类型重命名
//单链表接口定义
typedef struct SListNode
{SLTDataType data;struct SListNode* next;
}SLTNode;//打印
void SLTPrint(SLTNode* phead);
//创建结点
SLTNode* BuySListNode(SLTDataType x);//尾插
void SLTPushBack(SLTNode** pphead, SLTDataType x);
//头插
void SLTPushFront(SLTNode** pphead, SLTDataType x);//尾删
void SLTPopBack(SLTNode** pphead);
//头删
void SLTPopFront(SLTNode** pphead);//查找
SLTNode* SLTFind(SLTNode* phead, SLTDataType x);// 在pos之前插入x
void SLTInsert(SLTNode** pphead, SLTNode* pos, SLTDataType x);// 在pos以后插入x
void SLTInsertAfter(SLTNode** pphead,SLTNode* pos, SLTDataType x);// 删除pos位置
void SLTErase(SLTNode** pphead, SLTNode* pos);// 删除pos的后一个位置
void SLTEraseAfter(SLTNode** pphead, SLTNode* pos);

Single_linked_list.c

#include "Single_linked_list.h"//打印
void SLTPrint(SLTNode* phead)
{SLTNode* cur = phead;while (cur)//cur!=NULL为真{printf("%d ", cur->data);cur = cur->next;}printf("NULL\n");//打印尾结点的next结点NULL
}//创建结点
SLTNode* BuySListNode(SLTDataType x)
{SLTNode* newnode = (SLTNode*)malloc(sizeof(SLTNode));//创建一个新结点if (newnode == NULL)//创建失败返回错误结束程序{perror("malloc fail");exit(-1);}newnode->data = x;newnode->next = NULL;//将新结点的next结点置为NULLreturn newnode;
}//尾插
//传入结构体指针，用二级指针接收
void SLTPushBack(SLTNode** pphead, SLTDataType x)
{SLTNode* newnode = BuySListNode(x);//调用函数创建新结点//两种情况 头结点为空时和头结点不为空时if (*pphead == NULL){// 改变的结构体的指针，所以要用二级指针*pphead = newnode;}else{SLTNode* tail = *pphead;while (tail->next != NULL)//遍历链表到尾结点{tail = tail->next;}// 改变的结构体，用结构体的指针即可tail->next = newnode;}
}//头插
void SLTPushFront(SLTNode** pphead, SLTDataType x)
{SLTNode* newnode = BuySListNode(x);newnode->next = *pphead;// 改变的结构体的指针，所以要用二级指针*pphead = newnode;
}//尾删
void SLTPopBack(SLTNode** pphead)
{assert(*pphead);//判断*pphead是否为空//一个节点if ((*pphead)->next == NULL){free(*pphead);*pphead = NULL;}else//一个以上节点{SLTNode* tail = *pphead;while (tail->next->next)//遍历链表到尾结点{tail = tail->next;}free(tail->next);tail->next = NULL;}
}//头删
void SLTPopFront(SLTNode** pphead)
{assert(*pphead);//判断*pphead是否为空SLTNode* newhead = (*pphead)->next;free(*pphead);*pphead = newhead;
}//查找
SLTNode* SLTFind(SLTNode* phead, SLTDataType x) {SLTNode* cur = phead;while (cur != NULL&&cur->data != x ) {cur = cur->next;}if (cur == NULL) {printf("未查找到有效结点\n");exit(-1);}return cur;
}// 在pos之前插入x
void SLTInsert(SLTNode** pphead, SLTNode* pos, SLTDataType x) {SLTNode* newnode = BuySListNode(x);SLTNode* curPrev = *pphead;SLTNode* cur = SLTFind(curPrev,pos->data);if (curPrev == cur) {newnode->next = *pphead;*pphead = newnode;}else {while (curPrev->next != cur) {curPrev = curPrev->next;}newnode->next = cur;curPrev->next = newnode;}
}// 在pos以后插入x
void SLTInsertAfter(SLTNode** pphead,SLTNode* pos, SLTDataType x) {SLTNode* newnode = BuySListNode(x);SLTNode* temp = *pphead;SLTNode* cur = SLTFind(temp, pos->data);newnode->next = cur->next;cur->next = newnode;
}// 删除pos位置
void SLTErase(SLTNode** pphead, SLTNode* pos) {SLTNode* temp = *pphead;SLTNode* curPrev = *pphead;SLTNode* cur = SLTFind(temp, pos->data);if (curPrev == cur) {temp = cur->next;free(cur);cur = temp;}else {while (curPrev->next != cur) {curPrev = curPrev->next;}curPrev->next = cur->next;free(cur);cur = NULL;}
}// 删除pos的后一个位置
void SLTEraseAfter(SLTNode** pphead, SLTNode* pos) {SLTNode* temp = *pphead;SLTNode* cur = SLTFind(temp, pos->data);if (cur->next == NULL) {return;}else {temp = cur->next;cur->next = temp->next;free(temp);temp = NULL;}
}

Single_linked_list_test.c

void TestSList() {SLTNode* plist = NULL;SLTPushBack(&plist, 1);SLTPushBack(&plist, 2);SLTPushBack(&plist, 3);SLTPushBack(&plist, 4);SLTPushBack(&plist, 5);SLTPrint(plist);SLTNode* pos = BuySListNode(3);SLTInsert(&plist,pos, 6);free(pos);pos = NULL;SLTPrint(plist);pos = BuySListNode(3);SLTInsertAfter(&plist, pos, 7);free(pos);pos = NULL;SLTPrint(plist);pos = BuySListNode(6);SLTErase(&plist, pos);free(pos);pos = NULL;SLTPrint(plist);pos = BuySListNode(7);SLTErase(&plist, pos);free(pos);pos = NULL;SLTPrint(plist);pos = BuySListNode(3);SLTEraseAfter(&plist, pos);free(pos);pos = NULL;SLTPrint(plist);pos = BuySListNode(3);SLTEraseAfter(&plist, pos);free(pos);pos = NULL;SLTPrint(plist);pos = BuySListNode(1);SLTEraseAfter(&plist, pos);free(pos);pos = NULL;SLTPrint(plist);
}int main()
{TestSList();return 0;
}

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总结

无头单项非循环链表是链表的初始内容！
有点难度，但是不多，记住指针与多级指针之间的关系！
我相信大家也一定可以写出比我更好的代码！