dictionary.c

//===-- dictionary.c ---------------------------------------------*- C -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===---------------------------------------------------------------------===//
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct tree_node {
  const char *word;
  struct tree_node *left;
  struct tree_node *right;
} tree_node;

/* Given a char*, returns a substring that starts at the first
   alphabet character and ends at the last alphabet character, i.e. it
   strips off beginning or ending quotes, punctuation, etc. */

char *strip(char **word) {
  char *start = *word;
  int len = strlen(start);
  char *end = start + len - 1;

  while ((start < end) && (!isalpha(start[0])))
    start++;

  while ((end > start) && (!isalpha(end[0])))
    end--;

  if (start > end)
    return NULL;

  end[1] = '\0';
  *word = start;

  return start;
}

/* Given a binary search tree (sorted alphabetically by the word at
   each node), and a new word, inserts the word at the appropriate
   place in the tree.  */

void insert(tree_node *root, char *word) {
  if (root == NULL)
    return;

  int compare_value = strcmp(word, root->word);

  if (compare_value == 0)
    return;

  if (compare_value < 0) {
    if (root->left != NULL)
      insert(root->left, word);
    else {
      tree_node *new_node = (tree_node *)malloc(sizeof(tree_node));
      new_node->word = strdup(word);
      new_node->left = NULL;
      new_node->right = NULL;
      root->left = new_node;
    }
  } else {
    if (root->right != NULL)
      insert(root->right, word);
    else {
      tree_node *new_node = (tree_node *)malloc(sizeof(tree_node));
      new_node->word = strdup(word);
      new_node->left = NULL;
      new_node->right = NULL;
      root->right = new_node;
    }
  }
}

/* Read in a text file and storea all the words from the file in a
   binary search tree.  */

void populate_dictionary(tree_node **dictionary, char *filename) {
  FILE *in_file;
  char word[1024];

  in_file = fopen(filename, "r");
  if (in_file) {
    while (fscanf(in_file, "%s", word) == 1) {
      char *new_word = (strdup(word));
      new_word = strip(&new_word);
      if (*dictionary == NULL) {
        tree_node *new_node = (tree_node *)malloc(sizeof(tree_node));
        new_node->word = new_word;
        new_node->left = NULL;
        new_node->right = NULL;
        *dictionary = new_node;
      } else
        insert(*dictionary, new_word);
    }
  }
}

/* Given a binary search tree and a word, search for the word
   in the binary search tree.  */

int find_word(tree_node *dictionary, char *word) {
  if (!word || !dictionary)
    return 0;

  int compare_value = strcmp(word, dictionary->word);

  if (compare_value == 0)
    return 1;
  else if (compare_value < 0)
    return find_word(dictionary->left, word);
  else
    return find_word(dictionary->right, word);
}

/* Print out the words in the binary search tree, in sorted order.  */

void print_tree(tree_node *dictionary) {
  if (!dictionary)
    return;

  if (dictionary->left)
    print_tree(dictionary->left);

  printf("%s\n", dictionary->word);

  if (dictionary->right)
    print_tree(dictionary->right);
}

int main(int argc, char **argv) {
  tree_node *dictionary = NULL;
  char buffer[1024];
  char *filename;
  int done = 0;

  if (argc == 2)
    filename = argv[1];

  if (!filename)
    return -1;

  populate_dictionary(&dictionary, filename);
  fprintf(stdout, "Dictionary loaded.\nEnter search word: ");
  while (!done && fgets(buffer, sizeof(buffer), stdin)) {
    char *word = buffer;
    int len = strlen(word);
    int i;

    for (i = 0; i < len; ++i)
      word[i] = tolower(word[i]);

    if ((len > 0) && (word[len - 1] == '\n')) {
      word[len - 1] = '\0';
      len = len - 1;
    }

    if (find_word(dictionary, word))
      fprintf(stdout, "Yes!\n");
    else
      fprintf(stdout, "No!\n");

    fprintf(stdout, "Enter search word: ");
  }

  fprintf(stdout, "\n");
  return 0;
}