三种动态内存分配

分享几个例子，记住
1.calloc动态内存分配
#include<stdio.h>
#include <stdlib.h>

int main ()
{
int i,n;
int * pData;
printf ( "Amount of numbers to be entered: " );
scanf ( "%d",&i);
pData = ( int*) calloc (i,sizeof (int)); //i表示要开内存个数
if (pData==NULL)
exit (1);
for (n=0;n<i;n++)
{
printf ( "Enter number #%d: ",n);
scanf ( "%d",&pData
);
}
printf ( "You have entered: ");
for (n=0;n<i;n++) printf ( "%d ",pData
);
free (pData);
pData = NULL;
return 0;
}
2.malloc动态内存分配
/* malloc example: string 产生*/
#include <stdio.h>
#include <stdlib.h>
int main ()
{
int i,n;
char * buffer;
printf ( "How long do you want the string? " );
scanf ( "%d", &i);
buffer = ( char*) malloc (i+1);//i+1字符串末尾有“\0”
if (buffer==NULL) exit (1);

for (n=0; n<i; n++)
buffer
=rand()%26+ 'a';
buffer[i]= '\0';

printf ( "Random string: %s\n",buffer);
free (buffer);
buffer = NULL;//最好付空

return 0;
}
3.realloc动态分配内存
/* realloc example: 动态扩容*/
#include <stdio.h>
#include <stdlib.h>

int main ()
{
int input,n;
int count=0;
int * numbers = NULL;
int * more_numbers;

do {
printf ( "Enter an integer value (0 to end): " );
scanf ( "%d", &input);
count++;
//检查number大小，够就赋值过去，不够，重新分配，最后释放
more_numbers = ( int*) realloc (numbers, count * sizeof(int ));

if (more_numbers!=NULL) {
numbers=more_numbers;//改变指针指向
numbers[count-1]=input;//赋值
}
else {
free (numbers);//大空间分配失败，先释放空间，之后退出
puts ( "Error (re)allocating memory" );
exit (1);
}
} while (input!=0);

printf ( "Numbers entered: ");
for (n=0;n<count;n++) printf ( "%d ",numbers
);
free (numbers);//释放
return 0;
}