Programować każdy może (2)

#include "stdio.h"
#include "alloc.h"

#define MAXWORD 20
#define LETTER 'a'
#define DIGIT '0'

struct tnode { char *word;
               int count;
               struct tnode *left;
               struct tnode *right;
             };

main()
{ struct tnode *root, *tree();
  char word[MAXWORD];
  int t;

  root = NULL;
  while ((t = getword(word, MAXWORD)) != EOF )
        if (t == LETTER)
           root = tree(root, word);
  treeprint(root);
}

struct tnode *tree(p, w)
struct tnode *p;
char *w;
{ struct tnode *talloc();
  char *strsave();
  int count;

  if (p == NULL)
     { p = talloc();
       p->word = strsave(w);
       p->count = 1;
       p->left = p->right = NULL;
     }
  else
  if ((count = strcmp(w, p->word)) == 0 )
     p->count++;
  else
  if (count<0)
     p->left = tree(p->left, w);
  else
     p->right = tree(p->right, w);
  return (p);
}

treeprint(p)
struct tnode *p;
{ if (p != NULL)
     { treeprint(p->left);
       printf("%4d %s\n", p->count, p->word);
       treeprint(p->right);
     }
}

getword(w, lim)
char *w;
int lim;
{ int c, t;

  if (type(c = *w++ = gc()) != LETTER)
     { *w = '\0';
       return (c);
     }
  while (--lim > 0)
	{ t = type( c = *w++ = gc());
	  if ( t != LETTER && t != DIGIT)
	     { ungc(c);
	       break;
	     }
        }
	*(w-1) = '\0';
	return (LETTER);
}
int znak = EOF;

gc()
{ int c;
  if (znak != EOF)
     { c = znak;
       znak = EOF;
       return(c);
     }
  else
     return(getchar());
}

ungc(c)
int c;
{  znak = c; }

struct tnode *talloc()
{ return((struct tnode *) malloc(sizeof(struct tnode)));
}

char *strsave(w)
char *w;
{ char *p;
  p = malloc(MAXWORD);
  strcpy (p, w);
  return(p);
}

type(c)
int(c);
{ if (c>='a' && c<='z' || c>='A' && c<='Z')
     return(LETTER);
  else
  if (c>='0' && c<='9')
     return(DIGIT);
  else
     return(c);
}