C 反转字符串中的单词 "student a am i " --> "i am a student "

#include<stdio.h>

void cpy(char *s, char **o)
{
	while(**o!= '\0' && **o != ' ')
	{
		*s = **o;
		(*o)++;
		s++;
	}
	*s = '\0';
	return;
}

void cpy2(char **s,char *o)
{
	if(**s == '\0')
	{
		**s = ' ';
		(*s)++;
	}
	while(*o != '\0')
	{
		**s = *o;
		(*s)++;
		o++;
	}
	**s = '\0';
}

void test(char *p)
{
	static char *ep = p;
	char s[20];
	cpy(s,&p);
	if(*p != '\0')
		test(p+1);
	cpy2(&ep,s);
}

int main()
{	
	char a[] = "student a am i ";
	test(a);
	puts(a);
	return 0;
}