K and R C, Solution to Exercise 6-3:
K and R C Programs Exercises provides the solution to all the exercises in the C Programming Language (2nd Edition)
. You can learn and solve K&R C Programs Exercise.
C Program to Write a cross-referencer program 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. Read more about C Programming Language .
K and R C Programs Exercises provides the solution to all the exercises in the C Programming Language (2nd Edition)
. You can learn and solve K&R C Programs Exercise.C Program to Write a cross-referencer program 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. Read more about C Programming Language .
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* GitHub URL: https://github.com/snadahalli/cprograms/blob/master/knrc/knrc6_3.c
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/** Write a cross-referencer program 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
#include
#include
#include
char *dupstr(char *s) {
char *p = NULL;
if(s != NULL){
p = malloc(strlen(s) + 1);
if(p) {
strcpy(p, s);
}
}
return p;
}
int i_strcmp(const char *s, const char *t) {
int diff = 0;
char cs = 0;
char ct = 0;
while(diff == 0 && *s != ' ' && *t != ' ') {
cs = tolower((unsigned char)*s);
ct = tolower((unsigned char)*t);
if(cs < ct) {
diff = -1;
}
else if(cs > ct) {
diff = 1;
}
++s;
++t;
}
if(diff == 0 && *s != *t) {
if(*s == ' ') {
diff = -1;
}
else {
diff = 1;
}
}
return diff;
}
struct linelist {
struct linelist *next;
int line;
};
struct wordtree {
char *word;
struct linelist *firstline;
struct wordtree *left;
struct wordtree *right;
};
void printlist(struct linelist *list) {
if(list != NULL) {
printlist(list->next);
printf("%6d ", list->line);
}
}
void printtree(struct wordtree *node) {
if(node != NULL) {
printtree(node->left);
printf("%18s ", node->word);
printlist(node->firstline);
printf("n");
printtree(node->right);
}
}
struct linelist *addlink(int line) {
struct linelist *new = malloc(sizeof *new);
if(new != NULL) {
new->line = line;
new->next = NULL;
}
return new;
}
void deletelist(struct linelist *listnode) {
if(listnode != NULL) {
deletelist(listnode->next);
free(listnode);
}
}
void deleteword(struct wordtree **node) {
struct wordtree *temp = NULL;
if(node != NULL) {
if(*node != ' ') {
if((*node)->right != NULL) {
temp = *node;
deleteword(&temp->right);
}
if((*node)->left != NULL) {
temp = *node;
deleteword(&temp->left);
}
if((*node)->word != NULL) {
free((*node)->word);
}
if((*node)->firstline != NULL) {
deletelist((*node)->firstline);
}
free(*node);
*node = NULL;
}
}
}
struct wordtree *addword(struct wordtree **node, char *word, int line) {
struct wordtree *wordloc = NULL;
struct linelist *newline = NULL;
struct wordtree *temp = NULL;
int diff = 0;
if(node != NULL && word != NULL) {
if(NULL == *node) {
node = malloc(sizeof **node);
if(NULL != *node) {
(*node)->left = NULL;
(*node)->right = NULL;
(*node)->word = dupstr(word);
if((*node)->word != NULL) {
(*node)->firstline = addlink(line);
if((*node)->firstline != NULL) {
wordloc = *node;
}
}
}
}
else {
diff = i_strcmp((*node)->word, word);
if(0 == diff) {
newline = addlink(line);
if(newline != NULL) {
wordloc = *node;
newline->next = (*node)->firstline;
(*node)->firstline = newline;
}
}
else if(0 < diff) {
temp = *node;
wordloc = addword(&temp->left, word, line);
}
else {
temp = *node;
wordloc = addword(&temp->right, word, line);
}
}
}
if(wordloc == NULL) {
deleteword(node);
}
return wordloc;
}
char *char_in_string(char *s, int c) {
char *p = NULL;
/* if there's no data, we'll stop */
if(s != NULL) {
if(c != ' ') {
while(*s != ' ' && *s != c) {
++s;
}
if(*s == c) {
p = s;
}
}
}
return p;
}
char *tokenise(char **s, char *delims) {
char *p = NULL;
char *q = NULL;
if(s != NULL && *s != ' ' && delims != NULL) {
/* pass over leading delimiters */
while(NULL != char_in_string(delims, **s)) {
++*s;
}
if(**s != ' ') {
q = *s + 1;
p = *s;
while(*q != ' ' && NULL == char_in_string(delims, *q)) {
++q;
}
*s = q + (*q != ' ');
*q = ' ';
}
}
return p;
}
int NoiseWord(char *s)
{
int found = 0;
int giveup = 0;
char *list[] = {
"a",
"an",
"and",
"be",
"but",
"by",
"he",
"I",
"is",
"it",
"off",
"on",
"she",
"so",
"the",
"they",
"you"
};
int top = sizeof list / sizeof list[0] - 1;
int bottom = 0;
int guess = top / 2;
int diff = 0;
if(s != NULL) {
while(!found && !giveup) {
diff = i_strcmp(list[guess], s);
if(0 == diff) {
found = 1;
}
else if(0 < diff) {
top = guess - 1;
}
else {
bottom = guess + 1;
}
if(top < bottom) {
giveup = 1;
}
else {
guess = (top + bottom) / 2;
}
}
}
return found;
}
char *GetLine(char *s, int n, FILE *fp) {
int c = 0;
int done = 0;
char *p = s;
while(!done && --n > 0 && (c = getc(fp)) != EOF) {
if((*p++ = c) == 'n') {
done = 1;
}
}
*p = ' ';
if(EOF == c && p == s) {
p = NULL;
}
else {
p = s;
}
return p;
}
#define MAXLINE 8192
int main(void) {
static char buffer[MAXLINE] = {0};
char *s = NULL;
char *word = NULL;
int line = 0;
int giveup = 0;
struct wordtree *tree = NULL;
char *delims = " tnrafv!"%^&*()_=+{}[]\|/,.<>:;#~?";
while(!giveup && GetLine(buffer, sizeof buffer, stdin) != NULL) {
++line;
s = buffer;
while(!giveup && (word = tokenise(&s, delims)) != NULL) {
if(!NoiseWord(word)) {
if(NULL == addword(&tree, word, line)) {
printf("Error adding data into memory. Giving up.n");
giveup = 1;
}
}
}
}
if(!giveup) {
printf("%18s Line Numbersn", "Word");
printtree(tree);
}
deleteword(&tree);
return 0;
}
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