指標是C語言的精華，也是c中最難的部分；為了鍛鍊和提高自己對指標的理解，特在結構體中巢狀一級指標和二級指標來加深對。

#include<stdio.h>
#include <string.h>
#include<stdlib.h>
#define false 0
#define true 1

//結構體型別，每個導師有三個學生
typedef struct Tea
    {
    char *tName; //導師名字，需要動態分配空間char *====>char
    char **stu;  //三個學生，需要動態分配空間，堆區陣列
    int age;
    }Teacher;

//在createTeacher中分配空間
 

//n1 =3; //導師個數
//n2 = 3 //學生
int createTeacher(Teacher **p, int n1, int n2)
    {
    int len=0;
    int i,j,k;   //分配3個Student資訊
    *p = (Teacher*)malloc (sizeof(Teacher)*3);

    for (i=0;i<n1;i++)  //分配3個導師的地址空間
        {
        (*p)[i].tName=(char *)malloc (sizeof(char)*20);  
        if ((*p)[i].tName == NULL)
        {
          return
 
 false;
        }
        } 

    //(*p)->stu=(char **)malloc (sizeof(char*)*3);
    for (j=0;j<n2;j++)
        {
         (*p)[j].stu=(char **)malloc (sizeof(char)*3);
         if ((*p)[j].stu == NULL)
         {
           return false;
         }
         for (k=0;k<3;k++)
         {
         (*p)[j].stu[k]=(char
 
 *)malloc (sizeof(char)*20);
         if ((*p)[j].stu[k] == NULL)
             {
             return false;
             }
         }
        }
    return true;
    }


//給成員賦值
void initTeacher(Teacher *p, int n1, int n2)
    {
      int i,j,k=0;  //
      if (p == NULL)
      {
        printf ("error\n");
      }
      //n1 =3; //導師個數
      //n2 = 3 //學生
     puts ("-----導師賦值------");
     for (i=0;i<n1;i++)
     {
        char *buf[]={"王教授","陸教授","田導師"};
        p[i].age=22+i;
        //printf ("%d",p[i].age);
        strcpy (p[i].tName,buf[i]);
    //  printf ("%s",p[i].tName);
        for (j=0;j<n2;j++)
        {

          char *arr[]={"小黎","小田","小張","小王","小胡","小范",
              "小楊","小石","小柯"};
          strcpy (p[i].stu[j],arr[k]);
          ++k;
        //  printf ("%s\n",p[i].stu[j]);
        }
     }
    }

//列印結構體成員資訊
void printTeacher(Teacher *p, int n1, int n2)
    {
      int i,j;
      if (p == NULL)
      {
       printf ("error\n");
      }

      for (i=0;i<n1;i++)
      {
        printf ("\t\t%s\n",p[i].tName);  //導師
        for (j=0;j<n2;j++)
        {
           printf ("\t%s",p[i].stu[j]);
        }
        putchar('\n');
        printf ("\t\t%d\n\n",p[i].age);
      }
    }

//根據導師名字排序, 降序
void sortTeacher(Teacher *p, int n)
    {
      Teacher t1;
      int i,j;
       if (p==NULL)
       {
         printf ("error\n");
       }
       for (i=0;i<n-1;i++)
       {
         for (j=i+1;j<n;j++)
         {
           if ((strcmp (p[i].tName,p[j].tName))>0)
           {
             t1=p[i];
             p[i]=p[j];
             p[j]=t1;
           }
         }
       }

    }

//釋放空間，在函式內部把p賦值為NULL
void freeTeacher(Teacher **p, int n1, int n2)
    {
       int i,j;
       if (p == NULL)
       {
         printf ("Empty\n");
       }
       else
           {
              for (i=0;i<n1;i++)
              {
                 for (j=0;j<n2;j++)
                 {
                   if (p[i]->stu[j]!=NULL)
                   {
                     free (p[i]->stu[i]);
                     p[i]->stu[j]=NULL;
                   }
                 }
                 if (p[i]->stu!= NULL)
                 {
                   free (p[i]->stu);
                   p[i]->stu=NULL;
                 }
              }
           }
    }
int main(void)
    {
    int ret = 0;
    int n1 = 3; //導師個數
    int n2 = 3; //學生
    Teacher *p = NULL;
    ret = createTeacher(&p, n1, n2);
    if (ret == false)
        {
        printf("createTeacher err:%d\n", ret);
        exit (EXIT_FAILURE);
        }

    initTeacher(p, n1, n2); //給成員賦值
    //列印成員，排序前
    printf("排序前：\n");
    printTeacher(p, n1, n2);
    //根據導師名字排序, 降序
    sortTeacher(p, n1);
    //列印成員，排序後
    printf("\n排序後：\n");
    printTeacher(p, n1, n2);
    //釋放空間，在函式內部把p賦值為NULL
    //freeTeacher(&p, n1, n2);
    system("pause");
    return 0;
    }

記憶體四區圖：