Function to achieve string in reverse

Function to achieve string in reverse

The title string required to achieve a simple function of reverse.

Function interface definition:

void f( char *p );

Function f p string pointed to perform reverse operation. Required function f defined in any array can not call any string functions.

Sample input:

Hello World!

Sample output:

!dlroW olleH

#include <stdio.h>
#define MAXS 20

void f( char *p );
void ReadString( char *s ); /* 由裁判实现，略去不表 */

int main()
{
    char s[MAXS];

    ReadString(s);
    f(s);
    printf("%s\n", s);

    return 0;
}
void f( char *p )
{
    int i=0,q=0,h,huan;
    while(p[i]!='\0')
        i++;
    h=i-1;
    while(q<=h)
    {
        huan=p[q];
        p[q]=p[h];
        p[h]=huan;
        q++;
        h--;
    }
    return ;
}