/* wordfreq.c; cpl6.5 */

#include <stdio.h>
#include <ctype.h>
#include <stdlib.h> /* for malloc() */

#define MAXWORD 100

struct tnode {		/* the tree node */
	char *word;		/* points to the word */
	short count;		/* number of occurrences */
	struct tnode *left;	/* left branch */
	struct tnode *right;/* right branch */
};

struct tnode *addtree(struct tnode *, char *);
void treeprint(struct tnode *);
struct tnode *talloc(void);
char *strdup(char *);
int getword(char *, int);
void error(char *);

/* word frequency count */
main()
{
	struct tnode *root;
	char word[MAXWORD];

	root = NULL;
	while (getword(word, MAXWORD) != EOF)
		if (isalpha(word[0]))
			root = addtree(root,word);
	treeprint(root);
	return 0;
}

/* addtree: add a node with w, at or below p */
struct tnode *addtree(struct tnode *p, char *w)
{
	int cond;

	if (p == NULL) {		/* a new word has arrived */
		p = talloc();		/* make a new node */
		if (p == NULL) error("addtree: memory allocation failure");
		p->word = strdup(w);/* copy new word to its own memory location */
		p->count = 1;		/* initialize count for new word */
		p->left = p->right = NULL;	/* new branches empty */
	}
	else if ((cond = strcmp(w, p->word)) == 0)
		p->count++;			/* repeated word */
	else if (cond < 0)		/* into left branch */
		p->left = addtree(p->left, w);
	else
		p->right = addtree(p->right, w);
	return p;
}

/* treeprint: in-order print of tree p */
void treeprint(struct tnode *p)
{
	if (p != NULL) {
		treeprint(p->left);
		printf("%4d %s\n", p->count, p->word);
		treeprint(p->right);
	}
}


/* talloc: make a tnode */
struct tnode *talloc(void)
{
	return (struct tnode *) malloc(sizeof(struct tnode));
}

char *strdup(char *s)   /* make a duplicate of s */
{
	char *p;

	p = (char *) malloc(strlen(s) + 1);	/* +1 for '\0' */
	if (p != NULL)
		strcpy(p, s);
	else
		error("strdup: memory allocation failure");
	return p;
}

/* getword: get next word or character from input */
int getword(char *word, int lim)
{
	int c;
	char *w = word;

	while (isspace(c = getchar()))
		;
	if (c != EOF)
		*w++ = c;
	if (!isalpha(c)) {
		*w = '\0';
		return c;
	}
	for ( ; --lim > 0; w++)
		if (!isalnum(*w = getchar())) {
			ungetc(*w, stdin);
			break;
		}
	*w = '\0';
	return word[0];
}

void error(char *s)
{
	printf("\n%s\n");
	exit(1);
}