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

char *string_reverse(char *dst, const char *src)
{
    if (src == NULL) return NULL;

    const char *src_start = src;
    char *dst_end = dst + strlen(src);
    *dst_end = '\0';

    while ((*--dst_end = *src_start++)) {
        ;
    }
    
    return dst;
}


int main(void) {

	char str[20] = "Hello World";
	char dst[20];
	puts(string_reverse(dst, str));

	return 0;
}