malloc动态分配多维数组

下面试自己写的三个测试程序,如果看懂了基本上动态分配多维数组就没什么问题啦:重点 1:深刻理解多维数组的概念,多维数组在内存中的分配情况,基本上动态分配也没什么问题的。然后还要注意一点的就是,释放是分配的逆过程!!!

#include <stdio.h>

#include <malloc.h>

#include <string.h>

 

void main(void)

{

       int i ;

       char (*p)[12] ; //[5][12]

       p = malloc(5 * sizeof(char ) * 12);     //申请5行的地址空间

 

       for(i = 0 ; i < 5 ; i++)

       {

              strcpy(*(p + i), "hello");

       }

 

       for(i = 0 ; i < 5 ;i++)

       {

              printf("%s " , *(p + i));

       }

       free(p);

}

 

程序2:

#include <stdio.h>

#include <malloc.h>

#include <string.h>

 

void main(void)

{

       int i;

       int j ;

       int num = 0 ;

       char **p ;//[5][12]

       p =(char **) malloc( 5 * sizeof(char *) );          

 

       for(i = 0 ; i < 5 ; i++)

       {

              p[i] = malloc(12 * sizeof(char));

       }

 

       for(j = 0 ; j < 5 ; j++)

       {

              num = 0 ;

              for(i = 0 ; i < 12 ; i++)

              {

                     p[j][i] = 'a' + num;

                     num++ ;

              }

       }

 

       for(j = 0 ; j < 5 ; j++)

       {

              for(i = 0 ; i < 12 ; i++)

              {

                     printf("%c" , p[j][i]);

              }

              printf(" ");

       }

 

       for(i = 0 ; i < 5 ; i++)

       {

              free(p[i]);

       }

       free(p);

}

 

程序3:

#include <stdio.h>

#include <malloc.h>

#include <string.h>

 

void main(void)

{

       char ***pStr;

       int i , j , k ;

       // 自己分配一个三维的[3][4][5]

      

       pStr = (char ***)malloc(3 * sizeof(char **));      //第一维

      

       //分配二维的

       for(i = 0 ; i < 3 ; i++)

       {

              *(pStr + i) = malloc(4 * sizeof(char *));

       }

 

       //分配三维

       for(i = 0 ; i < 3 ; i++)

       {

              for(j = 0 ; j < 4 ; j++)

              {

                     *(*(pStr + i) + j) = malloc(5 * sizeof(char));

              }

       }

 

       //使用分配的内存

       for(i = 0 ; i < 3 ; i++)

       {

              for(j = 0 ; j < 4 ; j++)

              {

                     for(k = 0 ; k < 5 ; k++)

                     {

                            pStr[i][j][k] = 'a' ;

                            printf("%c" , pStr[i][j][k]);

                     }

                     printf(" ");

              }

       }

      

       //释放第三维的内存

       for(i = 0 ; i < 3 ; i++)

       {

              for(j = 0 ; j < 4 ;j++)

              {

                     free((pStr[i][j]));

              }

       }

 

       //释放第二维的内存

       for(i = 0 ; i < 3 ; i++)

       {

              free(pStr[i]);

       }

 

       //释放第一维的内存

       free(pStr);

}

原文地址:https://www.cnblogs.com/bohaoist/p/4607194.html