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/* Exercise 6-3
* Write a cross-referencer that prints a list of all words in a document, and,
* for each word, a list of the line numbers on which it occurs.
* Remove noise words like "the," "and," and so on.
*/
#include <stdio.h>
#include <ctype.h>
#include <stdbool.h>
#include <string.h>
#include <stdlib.h>
#define MAXWORDSIZE 100
#define BLACKWORDS (sizeof(blacklist) / sizeof(blacklist[0]))
// Sorted word blacklist
char *blacklist[] = { "a", "and", "of", "the" };
bool checkchar(char c)
{
//return isalpha(c) || c == '\'';
return isalpha(c);
}
int getword(char *dest, size_t max)
{
char c;
char *w = dest;
while (!checkchar(c = getchar()) && c != EOF) {
if (c == '\n') {
goto exit;
}
}
if (c == EOF) {
goto exit;
}
*w++ = tolower(c);
for (; --max; w++) {
if (!checkchar(c = getchar())) {
break;
}
*w = tolower(c);
}
exit:
*w = '\0';
return c;
}
bool checkword(char *w)
{
int l = 0;
int r = BLACKWORDS - 1;
while (l <= r) {
int m = (l + r) / 2;
int compare = strcmp(w, blacklist[m]);
if (compare == 0) {
return true;
}
if (compare < 0) {
r = m - 1;
} else {
l = m + 1;
}
}
return false;
}
// Tree stuff
typedef struct occur_list {
unsigned line;
struct occur_list *next;
} occur_t;
typedef struct tree_node {
char word[MAXWORDSIZE];
occur_t *occurs;
struct tree_node *left;
struct tree_node *right;
} treenode_t;
occur_t *occur_insert(occur_t *l, unsigned line)
{
occur_t *new = (occur_t *)malloc(sizeof(occur_t));
new->next = l ? l->next : new;
new->line = line;
if (l) {
l->next = new;
}
return new;
}
void occur_print(occur_t *l)
{
if (!l) {
return;
}
occur_t *n = l->next;
for (; n; n = n->next) {
printf("%d ", n->line);
if (n == l) {
break;
}
}
}
treenode_t *tree_insert(treenode_t *t, char *word, unsigned line)
{
if (!t) {
treenode_t *node = (treenode_t *)malloc(sizeof(treenode_t));
strcpy(node->word, word);
node->left = node->right = NULL;
node->occurs = occur_insert(node->occurs, line);
return node;
}
int compare = strcmp(t->word, word);
if (compare == 0) {
t->occurs = occur_insert(t->occurs, line);
return t;
}
treenode_t **branch = compare > 0 ? &t->left : &t->right;
*branch = tree_insert(*branch, word, line);
return t;
}
void tree_print_words(treenode_t *t, unsigned longest)
{
if (!t) {
return;
}
tree_print_words(t->left, longest);
printf("%*.*s: ", -longest, longest, t->word);
occur_print(t->occurs);
putchar('\n');
tree_print_words(t->right, longest);
}
int main()
{
char word[MAXWORDSIZE];
char c;
treenode_t *root = NULL;
unsigned line = 1;
size_t longest = 0;
unsigned i = 0;
while ((c = getword(word, MAXWORDSIZE)) != EOF) {
if (word[0] == '\0' || checkword(word)) {
goto next_word;
}
size_t wlen = strlen(word);
if (wlen > longest) {
longest = wlen;
}
root = tree_insert(root, word, line);
// This goto can be replaced by a for loop
next_word:
if (c == '\n') {
line++;
}
}
tree_print_words(root, longest);
}
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