1、链表之增、删、查实现（C语言）

一、功能描述：

可以创建节点并添加到链表中、查看链表中的所有节点、并可以删除特定的节点

二、代码实现

1、主函数main主要实现的是从后台键入不同的字符，执行对应的函数来实现特定的操作代码如下：

int main(char argc, char *argv[])
{
    char c;
    while ()
    {
        c = getchar();                //键入一个字符
//        printf("c = %c\n",c);

        printf("Usage:\n");
        printf("<l> List all the notes\n");
        printf("<a> Add a node to chains\n");
        printf("<d> Delete a node from chains\n");
        printf("<q> quit\n");
        printf("Enter the choise: \n");
        switch (c)
        {
            case 'l' :
            {
                list_all_notes();    //显示链表中所有的节点
                break;
            }
            case 'a' :
            {
                add_a_node();    //链表中添加一个节点
                break;
            }
            case 'd' :
            {
                delete_a_node();    //删除链表中的一个节点
                break;
            }
            case 'q' :                //退出死循环
            {
                return ;
                break;
            }
            defaut :
            {
                break;
            }
        }
    }
    return ;
}

2、add_a_node的主要作用创建一个节点，并初始化（节点分配内存、初始化节点name），最后调用add_note_to_chains函数把该节点添加到链表中，代码如下：

 void add_a_node()
 {
     char *str;                //用来存放节点名字
     char name[];        //临时变量，键盘设置新节点的名字
     PT_Node ptNew;        //指针变量，指向新的节点

     printf("Please enter name of node to be added : ");
     scanf("%s", name);        //给新添加的节点取一个名字

     str = malloc(strlen(name) + );    //为节点的名字分配空间
     strcpy(str, name);

     ptNew = malloc(sizeof(T_Node));    //为新节点分配内存

     //初始化节点中的元素
     ptNew ->name = str;            //节点中的name指向str
     ptNew ->pre = NULL;
     ptNew ->next = NULL;

     add_note_to_chains(ptNew);    //把该节点添加到链表中
 }

3、add_note_to_chains主要实现的是把节点挂载到链表中，代码如下：

static void add_note_to_chains(PT_Node ptNew)
{
    PT_Node ptCur;
    if (g_ptNodeHead == NULL)
    {
        g_ptNodeHead = ptNew;//如果链表中没有一个节点，则头结点指向该节点
    }
    else
    {
        ptCur = g_ptNodeHead;
        while(ptCur ->next)    //遍历找到当前节点的next元素为空
        {
            ptCur = ptCur ->next;
        }

        ptCur->next = ptNew;    //把新的节点挂载到g_ptNodeHead链表中
        ptNew ->pre = ptCur;

    }
}

4、delete_a_node函数的主要功能是通过键入的name，索引到链表中对应的节点地址，最后调用delete_node函数删除（卸载）链表中对应的节点，代码如下：

static void delete_a_node()
{
    PT_Node ptFindName;
    char name[];

    printf("Please enter the name of node to be deleted :");
    scanf("%s", name);

    ptFindName = get_name(name);    //通过名字获得对应节点地址
    if (ptFindName == NULL)
    {
        printf("Don't have this node\n");
        return;
    }

    delete_node(ptFindName);        //删除链表中对应的节点
}

5、get_name函数的作用是通过节点name在链表中索引到其对应的节点地址，代码如下：

PT_Node get_name(char *name)
{
    PT_Node ptCar;
    if (g_ptNodeHead == NULL)
    {
        return NULL;
    }
    else
    {
        ptCar = g_ptNodeHead;
        do{
            if (strcmp (ptCar->name, name) == )
            {
                    printf("find \'%s\' from chain\n",name);
                    return ptCar;
            }
            else
            {
                ptCar = ptCar->next;
            }
        }while (ptCar);

        printf("don't find \'%s\' from chain\n",name);
        return NULL;
    }
}

6、delete_node函数的主要作用是卸载链表中对应的节点，卸载细节如下图，其中ptCar为当前要被卸载的节点、ptPre为前一个节点、ptNext为后一个节点

对应代码如下：

static void delete_node(PT_Node ptDel)
{
    PT_Node ptCar;
    PT_Node ptPre;
    PT_Node ptNext;
    if (g_ptNodeHead == ptDel)
    {
        g_ptNodeHead = ptDel->next;
//        return;
    }
    else{
        ptCar = g_ptNodeHead ->next;
//        printf("1111111111111\n");
        while(ptCar)
        {
            if (ptCar == ptDel)
            {
                //从链表中删除
                ptPre    = ptCar ->pre;
                ptNext  = ptCar ->next;
                ptPre->next = ptNext;
//                printf("22222222\n");
                if(ptNext)
                {
                    ptNext ->pre = ptPre;
                }
                break;
            }
            else
            {
                ptCar = ptCar->next;
//                printf("333333\n");
            }
        }
    }
    free(ptDel->name);    //释放节点名字占用的内存
    free(ptDel);            //释放节点占用的内存
}

7、list_all_notes显示链表中的所用节点，代码如下：

static void list_all_notes()
{
    PT_Node ptCar;
    ptCar = g_ptNodeHead;
    int i = ;
    if (g_ptNodeHead == NULL)
    {
        printf("\n");
        printf("There is no node in chain list!\n");
        printf("\n");
    }
    while(ptCar)
    {
        printf("%02d : %s\n", i++, ptCar ->name);
        ptCar = ptCar ->next;
    }
}

8、完整代码实现

 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>

 //定义一个节点
 typedef struct T_NODE{
     char *name;
     struct T_NODE *pre;
     struct T_NODE *next;
 }T_Node, *PT_Node;

 static PT_Node g_ptNodeHead;    //链表头

 static void add_note_to_chains(PT_Node ptNew)
 {
     PT_Node ptCur;
     if (g_ptNodeHead == NULL)
     {
         g_ptNodeHead = ptNew;//如果链表中没有一个节点，则头结点指向该节点
     }
     else
     {
         ptCur = g_ptNodeHead;
         while(ptCur ->next)    //遍历找到当前节点的next元素为空
         {
             ptCur = ptCur ->next;
         }

         ptCur->next = ptNew;    //把新的节点挂载到g_ptNodeHead链表中
         ptNew ->pre = ptCur;

     }
 }

 void add_a_node()
 {
     char *str;                //用来存放节点名字
     char name[];        //临时变量，键盘设置新节点的名字
     PT_Node ptNew;        //指针变量，指向新的节点

     printf("Please enter name of node to be added : ");
     scanf("%s", name);        //给新添加的节点取一个名字

     str = malloc(strlen(name) + );    //为节点的名字分配空间
     strcpy(str, name);

     ptNew = malloc(sizeof(T_Node));    //为新节点分配内存

     //初始化节点中的元素
     ptNew ->name = str;            //节点中的name指向str
     ptNew ->pre = NULL;
     ptNew ->next = NULL;

     add_note_to_chains(ptNew);    //把该节点添加到链表中
 }

 PT_Node get_name(char *name)
 {
     PT_Node ptCar;
     if (g_ptNodeHead == NULL)
     {
         return NULL;
     }
     else
     {
         ptCar = g_ptNodeHead;
         do{
             if (strcmp (ptCar->name, name) == )
             {
                     printf("find \'%s\' from chain\n",name);
                     return ptCar;
             }
             else
             {
                 ptCar = ptCar->next;
             }
         }while (ptCar);

         printf("don't find \'%s\' from chain\n",name);
         return NULL;

     }

 }

 static void delete_node(PT_Node ptDel)
 {
     PT_Node ptCar;
     PT_Node ptPre;
     PT_Node ptNext;
     if (g_ptNodeHead == ptDel)
     {
         g_ptNodeHead = ptDel->next;
 //        return;
     }
     else{
         ptCar = g_ptNodeHead ->next;
 //        printf("1111111111111\n");
         while(ptCar)
         {
             if (ptCar == ptDel)
             {
                 //从链表中删除
                 ptPre    = ptCar ->pre;
                 ptNext  = ptCar ->next;
                 ptPre->next = ptNext;
 //                printf("22222222\n");
                 if(ptNext)
                 {
                     ptNext ->pre = ptPre;
                 }
                 break;
             }
             else
             {
                 ptCar = ptCar->next;
 //                printf("333333\n");
             }
         }
     }
     free(ptDel->name);    //释放节点名字占用的内存
     free(ptDel);            //释放节点占用的内存
 }

 static void delete_a_node()
 {
     PT_Node ptFindName;
     char name[];

     printf("Please enter the name of node to be deleted :");
     scanf("%s", name);

     ptFindName = get_name(name);    //通过名字获得对应节点地址
     if (ptFindName == NULL)
     {
         printf("Don't have this node\n");
         return;
     }

     delete_node(ptFindName);        //删除链表中对应的节点
 }

 static void list_all_notes()
 {
     PT_Node ptCar;
     ptCar = g_ptNodeHead;
     int i = ;
     if (g_ptNodeHead == NULL)
     {
         printf("\n");
         printf("There is no node in chain list!\n");
         printf("\n");
     }
     while(ptCar)
     {
         printf("%02d : %s\n", i++, ptCar ->name);
         ptCar = ptCar ->next;
     }
 }

 int main(char argc, char *argv[])
 {
     char c;
     while ()
     {
         c = getchar();                    //键入一个字符
 //        printf("c = %c\n",c);

         printf("Usage:\n");
         printf("<l> List all the notes\n");
         printf("<a> Add a node to chains\n");
         printf("<d> Delete a node from chains\n");
         printf("<q> quit\n");
         printf("Enter the choise: \n");
         switch (c)
         {
             case 'l' :
             {
                 list_all_notes();        //显示链表中所有的节点
                 break;
             }
             case 'a' :
             {
                 add_a_node();        //链表中添加一个节点
                 break;
             }
             case 'd' :
             {
                 delete_a_node();        //删除链表中的一个节点
                 break;
             }
             case 'q' :                    //退出死循环
             {
                 return ;
                 break;
             }
             defaut :
             {        

                 break;
             }
         }
     }
     return ;
 }