C USES the malloc function to apply an example of a two dimensional dynamic array

C USES the malloc function to apply an example of a 2 - dimensional dynamic array

C language in the program running dynamic application and release of memory 10 minutes convenient, 1 - dimensional array application and release relatively simple.

Sample one

#include <stdio.h> 
int main() 
{ 
  char * p=(char *)malloc(sizeof(char)*5);// Applications include 5 An array of characters  
  free(p); 
  return 0; 
} 

Is it so easy to apply for 2-d dynamic memory? The answer is no. There are several ways to apply a 2 - dimensional array

Sample two

/*  To apply for 1 a 5 line 3 A character array of columns */ 
char **p=NULL;int i; 
p=(char ** )malloc(sizeof(char *)*5); 
for(i=0;i<5;i++) 
  p[i]=malloc(sizeof(char)*3) ;  

The advantage of this approach is that both the rows and columns are mutable, but you must release them multiple times. Release p[n] first, then p

/* Free memory */ 
for(i=0;i<5;i++) 
   free(p[i]); 
free(p); 

Sample three

/* Use a pointer to an array to request memory */ 
char (*p)[3]=(char(*)[3])malloc(sizeof(char)*5*3)//p is 1 Individual point includes 3 Pointer to an array of elements  

The memory allocated in this way only needs to be freed once

free(p); 

The disadvantage of this approach is that columns are immutable!

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