Mega Code Archive
Scan a file and print out a list of words in ASCII order
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/*
Practical C Programming, Third Edition
By Steve Oualline
Third Edition August 1997
ISBN: 1-56592-306-5
Publisher: O'Reilly
*/
#include <stdio.h>
#include <ctype.h>
#include <string.h>
#include <stdlib.h>
struct node {
struct node *left; /* tree to the left */
struct node *right; /* tree to the right */
char *word; /* word for this tree */
};
/* the top of the tree */
static struct node *root = NULL;
/*
* memory_error -- write error and die *
*/
void memory_error(void)
{
fprintf(stderr, "Error:Out of memory\n");
exit(8);
}
/*
* save_string -- save a string on the heap *
* *
* Parameters *
* string -- string to save *
* *
* Returns *
* pointer to malloc-ed section of memory with *
* the string copied into it. *
*/
char *save_string(char *string)
{
char *new_string; /* where we are going to put string */
new_string = malloc((unsigned) (strlen(string) + 1));
if (new_string == NULL)
memory_error();
strcpy(new_string, string);
return (new_string);
}
/*
* enter -- enter a word into the tree *
* *
* Parameters *
* node -- current node we are looking at *
* word -- word to enter *
*/
void enter(struct node **node, char *word)
{
int result; /* result of strcmp */
char *save_string(char *); /* save a string on the heap */
/*
* If the current node is null, we have reached the bottom
* of the tree and must create a new node.
*/
if ((*node) == NULL) {
/* Allocate memory for a new node */
(*node) = malloc(sizeof(struct node));
if ((*node) == NULL)
memory_error();
/* Initialize the new node */
(*node)->left = NULL;
(*node)->right = NULL;
(*node)->word = save_string(word);
return;
}
/* Check to see where the word goes */
result = strcmp((*node)->word, word);
/* The current node already contains the word, no entry necessary */
if (result == 0)
return;
/* The word must be entered in the left or right sub-tree */
if (result < 0)
enter(&(*node)->right, word);
else
enter(&(*node)->left, word);
}
/*
* scan -- scan the file for words *
* *
* Parameters *
* name -- name of the file to scan *
*/
void scan(char *name)
{
char word[100]; /* word we are working on */
int index; /* index into the word */
int ch; /* current character */
FILE *in_file; /* input file */
in_file = fopen(name, "r");
if (in_file == NULL) {
fprintf(stderr, "Error:Unable to open %s\n", name);
exit(8);
}
while (1) {
/* scan past the whitespace */
while (1) {
ch = fgetc(in_file);
if (isalpha(ch) || (ch == EOF))
break;
}
if (ch == EOF)
break;
word[0] = ch;
for (index = 1; index < sizeof(word); ++index) {
ch = fgetc(in_file);
if (!isalpha(ch))
break;
word[index] = ch;
}
/* put a null on the end */
word[index] = '\0';
enter(&root, word);
}
fclose(in_file);
}
/*
* print_tree -- print out the words in a tree *
* *
* Parameters *
* top -- the root of the tree to print *
*/
void print_tree(struct node *top)
{
if (top == NULL)
return; /* short tree */
print_tree(top->left);
printf("%s\n", top->word);
print_tree(top->right);
}
int main(int argc, char *argv[])
{
if (argc != 2) {
fprintf(stderr, "Error:Wrong number of parameters\n");
fprintf(stderr, " on the command line\n");
fprintf(stderr, "Usage is:\n");
fprintf(stderr, " words 'file'\n");
exit(8);
}
scan(argv[1]);
print_tree(root);
return (0);
}
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