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

int main(int argc, const char *argv[])
{
     char *src="hello world";
    char *dest=NULL;

    int len = strlen(src);

    dest=(char *)malloc(len+1);
    if(NULL==dest)
    {
       printf("malloc is fail");
       return -1;
    }

    char *d=dest;
    char *s=&src[len-1];

    while(len--!=0)
        *d++=*s--;
        *d='\0';
    puts(dest);

    free(dest);
    dest=NULL;

    return 0;
}