动态内存分配实例

例子1、

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

int main()
{
int	*pi, *pi2;
pi = ( int * )malloc( 10 * sizeof( int ) );

if( pi == NULL )
printf( " out of memory!\n" );
else
printf( "malloc success!\n" );
//free( pi );
pi2 = pi;

for( int i = 0; i < 10; i++ )
*pi++ = 6;

for( int i = 0; i < 10; i++ )
printf( "%d = %d\n",i,*pi2++ );
}

打印结果：

wangkai@ubuntu:~/Test$ ./string
malloc success!
0 = 6
1 = 6
2 = 6
3 = 6
4 = 6
5 = 6
6 = 6
7 = 6
8 = 6
9 = 6
wangkai@ubuntu:~/Test$

实例二

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

int compare_integers( void const *a, void const * b )
{
register int const *pa = (int *)a;
register int const *pb = (int *)b;

return *pa > *pb ? 1 : *pa < *pb ? -1: 0;
}

int main()
{
int	*array;
int	n_values;
int	i;

printf( "How many values are there ?" );
if( scanf( "%d",&n_values ) != 1 || n_values <= 0 ){
printf( "Iligal number of values.\n" );
exit( EXIT_FAILURE );
}

array = (int *)malloc( n_values * sizeof( int ) );
if( array == NULL ){
printf( "Can't get memory for that many values.\n" );
exit( EXIT_FAILURE );
}

for( i = 0;i < n_values; i +=1 ){
printf( "?" );
if( scanf( "%d",array + i ) != 1 ) {
printf( "Error reading value #%d\n",i );
free( array );
exit( EXIT_FAILURE );
}

}

qsort( array,n_values,sizeof( int ),  compare_integers );

for( i = 0; i < n_values; i +=1 )
printf( "%d\n",*(array + i) );

free( array );
return EXIT_SUCCESS;

}

qsort包含在<stdlib.h>头文件中，此函数根据你给的比较条件进行快速排序，通过指针移动实现排序。排序之后的结果仍然放在原数组中。使用qsort函数必须自己写一个比较函数。

函数原型：

void qsort ( void * base, size_t num, size_t size, int ( * comparator ) ( const void *, const void * ) );