struct tnode *talloc(void);
char *strdup(char *);

/* 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 */
        p->word = strdup(w);
        p->count = 1;
        p->left = p->right = NULL;
    } else if ((cond = strcmp(w, p->word)) == 0)
        p->count++;     /* repeated word */
    else if (cond < 0)  /* less than into left subtree */
        p->left = addtree(p->left, w);
    else            /* greater than into right subtree */
        p->right = addtree(p->right, w);
    return p;
}