c语言实现单链表&二级指针在单链表的应用

c语言实现单链表

用C语言实现链表的头插，头删，尾插，尾删，查找节点，任意节点插入，和任意节点删除等功能
此代码运用的是二级指针实现单链表，所以在写代码时要注意参数类型。

关于二级指针和一级指针：

一级指针变量指向的内容是普通变量的值，二级指针变量指向的内容是一级指针变量的地址。
当你想对一个地址做修改的时候，就要用到二级指针。

完整代码

#define __CRT_SECURE_NO_WARNRINGS 1#include "slist.h"//初始化链表void InitLinkList(ListNode** ppList){    assert(ppList);    *ppList = NULL;}//打印链表void PrintList(ListNode* pList){    ListNode* cur = pList;    while (cur){        printf("%d ", cur->data);            cur= cur->next;    }    printf("\n");    return;}//申请一个新节点ListNode* Buynewnode(DataType x){    ListNode* newNode = NULL;    newNode = (ListNode*)malloc(sizeof(ListNode));//开辟新节点，强制类型转换    if (newNode == NULL){        printf("out of memory \n");//溢出    }    else{        newNode->data = x;        newNode->next = NULL;    }    return newNode;}//尾插void PushBack(ListNode** ppList, DataType x){    assert(ppList);    if (*ppList == NULL){        *ppList = Buynewnode(x);    }    else{        ListNode* ppcur = NULL;        ppcur = *ppList;        while (ppcur->next)        {            ppcur = ppcur->next;        }        ppcur->next = Buynewnode(x);    }}//尾删void PopBack(ListNode** ppList){    assert(ppList);    ListNode* cur = *ppList;    if (cur == NULL){        return ;    }    if (cur->next==NULL){        free(cur);        cur = NULL;    }    else{        while (cur->next->next){            cur = cur->next;        }        free(cur->next);        cur->next = NULL;    }}//头插void PushFront(ListNode** ppList, DataType x){    assert(ppList);    ListNode* pFirst=NULL;    if (*ppList==NULL){        *ppList = Buynewnode(x);    }    else{        pFirst = Buynewnode(x);        pFirst->next = *ppList;        *ppList = pFirst;        }}//头删void PopFront(ListNode** ppList){    assert(ppList);    if (*ppList == NULL){        return;    }    else{        ListNode* cur = *ppList;        *ppList = (*ppList)->next;        free(cur);        cur = NULL;    }}//查找表中元素xListNode* Find(ListNode* pList, DataType x){    assert(pList);    ListNode* cur = pList;    //if (cur == NULL){    //  return ;    //}    while (cur){        if (cur->data == x)            break;        cur = cur->next;        }    return cur;}// 在pos的前面插入一个节点x void Insert(ListNode** ppList, ListNode* pos, DataType x){    assert(ppList);    assert(pos);    DataType tmp=0;    ListNode* newnode = Buynewnode(x);    if (*ppList == NULL){        PushBack(ppList, x);    }    else if (pos == NULL){        return;    }    else{        newnode->next =pos->next;        pos->next = newnode;        tmp = pos->data;        pos->data = newnode->data;        newnode->data = tmp;    }}//删除pos前一位置节点void Erase(ListNode** ppList, ListNode* pos){    assert(ppList);    assert(pos);    ListNode* cur = *ppList;    if (cur == NULL){        return;    }    else{        while (cur->next!=pos&&cur){            cur = cur->next;        }        cur->next = pos->next;        free(pos);        pos = NULL;    }}

测试函数

#include "slist.h"//测试void test1(){    ListNode *list;    InitLinkList(&list);    printf("插入数据\n");    PushBack(&list, 1);    PushBack(&list, 2);    PushBack(&list, 3);    PushBack(&list, 4);    PushBack(&list, 5);    PushBack(&list, 6);    PrintList(list);    printf("从尾部删除数据后\n");    PopBack(&list);    PopBack(&list);    PrintList(list);    ListNode* _find;    _find=Find(list, 2);    printf("找到节点pos：%d\n", _find->data);    ListNode* pos = _find;    printf("在pos前插入节点:\n");    Insert(&list,pos, 7);    PrintList(list);    printf("删除pos前节点:\n");    Erase(&list, pos);    PrintList(list);}void test2(){    ListNode* List;    InitLinkList(&List);    printf("头插数据\n");    PushFront(&List, 1);    PushFront(&List, 2);    PushFront(&List, 3);    PushFront(&List, 4);    PrintList(List);    printf("头删数据后");    PopFront(&List);    PopFront(&List);    PopFront(&List);    PopFront(&List);    PrintList(List);}int main(){    test1();    //test2();    system("pause");    return 0;}

头文件

#define __CRT_SECURE_NO_WARNRINGS 1#ifndef __SLIST_H__#define __SLIST_H__#include <stdio.h>#include <stdlib.h>#include <assert.h>typedef int DataType;typedef struct ListNode{    DataType data;    struct ListNode* next;}ListNode;void InitLinkList(ListNode** ppList);void PrintList(ListNode* pList);ListNode* Buynewnode(DataType x);void PushBack(ListNode** ppList, DataType x);void PopBack(ListNode** ppList);void PushFront(ListNode** ppList, DataType x);void PopFront(ListNode** ppList);ListNode* Find(ListNode* pList, DataType x);// 在pos的前面插入一个节点x void Insert(ListNode** ppList, ListNode* pos, DataType x);void Erase(ListNode** ppList, ListNode* pos);#endif //__SLIST_H__

测试结果：

test1:

test2: