C言語のコピー関数を実現し、コピーされた文字列を逆順にします.ライブラリ関数は使用できません.他の変数は定義できません.

/*
   C       ,       ，               from  1234, 
   to  4321 void strcyp(char * to,const char * from)    ：   
    ：                  。
*/
#include <cstdio>
#include <cstdlib>

void strcyp(char *to, const char * from);

int main()
{
    char *in = "asdf!1234+567!@#$%^&*()_+8*90?";
    char *out;
    
    int len = 1;
    char *head;
    
    head = in;
    while (*head != '\0')
    {
        len++;
        head++;
    }
    
    out = (char *)malloc(sizeof(char) * (len + 1));
    strcyp(out, in);

    head = in;
    while (*head != '\0')
      printf("%c", *head++);
    printf("
");
    
    head = out;
    while (*head != '\0')
      printf("%c", *head++);
    printf("
");
    
    delete out;
    return 0;
}

void strcyp(char *to, const char * from)
{
    /*    */
    if (from == NULL || *from == '\0'|| from == to)
		return -1;
    
    /*   to           from[0]*/  
    *to++ = *from++;
    
    /*  from       ,   to      -1*/
    while (*from != '\0')
	{
		from++;
		*to++ = -1;
	}
    from--;
	*to-- = '\0';
    
    /*   from         '-1'     */
    while (*to == -1)
		to--;
    
	while (*to != '\0')
		*to++ = *from--;
}