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/* wf1 - print word frequencies; uses structures */

struct node {
        int count;              /* frequency count */
        struct node *left;      /* left subtree */
        struct node *right;     /* right subtree */
        char *word;             /* word itself */
} words[2000];
int next;               /* index of next free entry in words */

struct node *lookup();

main()
{
        struct node *root;
        char word[20];

        root = 0;
        next = 0;
        while (getword(word))
                lookup(word, &root)->count++;
        tprint(root);
        return 0;
}

/* err - print error message s and die  */
err(s)
char *s;
{
        printf("? %s\n", s);
        exit(1);
}

/* getword - get next input word into buf, return 0 on EOF */
int getword(buf)
char *buf;
{
        char *s;
        int c;

        while ((c = getchar()) != -1 && isletter(c) == 0)
                ;
        for (s = buf; c = isletter(c); c = getchar())
                *s++ = c;
        *s = 0;
        if (s > buf)
                return (1);
        return (0);
}

/* isletter - return folded version of c if it is a letter, 0 otherwise */
int isletter(c)
int c;
{
        if (c >= 'A' && c <= 'Z')
                c += 'a' - 'A';
        if (c >= 'a' && c <= 'z')
                return (c);
        return (0);
}

/* lookup - lookup word in tree; install if necessary */
struct node *lookup(word, p)
char *word;
struct node **p;
{
        int cond;
        char *malloc();

        if (*p) {
                cond = strcmp(word, (*p)->word);
                if (cond < 0)
                        return lookup(word, &(*p)->left);
                else if (cond > 0)
                        return lookup(word, &(*p)->right);
                else
                        return *p;
        }
        if (next >= 2000)
                err("out of node storage");
        words[next].count = 0;
        words[next].left = words[next].right = 0;
        words[next].word = malloc(strlen(word) + 1);
        if (words[next].word == 0)
                err("out of word storage");
        strcpy(words[next].word, word);
        return *p = &words[next++];
}

/* tprint - print tree */
tprint(tree)
struct node *tree;
{
        if (tree) {
                tprint(tree->left);
                printf("%d\t%s\n", tree->count, tree->word);
                tprint(tree->right);
        }
}

/* strcmp - compare s1 and s2, return <0, 0, or >0 */
int strcmp(s1, s2)
char *s1, *s2;
{
        while (*s1 == *s2) {
                if (*s1++ == 0)
                        return 0;
                ++s2;
        }
        if (*s1 == 0)
                return -1;
        else if (*s2 == 0)
                return 1;
        return *s1 - *s2;
}