feat: Added a program that prints words in alphabetical order using binary tree data structure

data_structures/binary_trees/words_alphabetical.c

@@ -0,0 +1,226 @@
+/**
+ * @file
+ * @brief Printing the words contained in a file "file.txt" in alphabetical
+ * order and also their frequencies in to another file "wordcount.txt"
+ */
+#include <ctype.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+/**
+ * Structure defining a node in the binary tree
+ */
+struct Node
+{
+    char *word;
+    unsigned int frequency;
+    struct Node *left;
+    struct Node *right;
+};
+
+struct Node *readWordsInFileToTree(FILE *file, struct Node *root);
+struct Node *addWordToTree(char *word, struct Node *currentNode);
+void writeContentOfTreeToFile(struct Node *node, FILE *file);
+char *getPointerToWord(char *word);
+struct Node *allocateMemoryForNode();
+void closeFile(FILE *file);
+void freeTreeMemory(struct Node *node);
+void endProgramAbruptly(char *errorMessage);
+
+int main()
+{
+    struct Node *root = NULL;
+    FILE *file = NULL;
+
+    file = fopen("file.txt", "r");
+    if (file == NULL)
+        endProgramAbruptly("file: 'file.txt' not found");
+
+    root = readWordsInFileToTree(file, root);
+    closeFile(file);
+
+    file = fopen("wordcount.txt", "a");
+    fprintf(file, "%-5s \t %9s \t %s \n", "S/N", "FREQUENCY", "WORD");
+    writeContentOfTreeToFile(root, file);
+    closeFile(file);
+
+    freeTreeMemory(root);
+
+    return 0;
+}
+
+/**
+ * Read words from file to binary tree
+ * @param file file to be read from
+ * @param root top node of tree
+ */
+struct Node *readWordsInFileToTree(FILE *file, struct Node *root)
+{
+    char *inputString = (char *)malloc(46 * sizeof(char));
+    // longest english word = 45 chars
+    // +1 for '\0' = 46 chars
+    char inputChar;
+    bool isPrevCharAlpha = false;
+    int pos = 0;
+    while ((inputChar = fgetc(file)) != EOF)
+    {
+        if (pos > 0)
+            isPrevCharAlpha = isalpha(inputString[pos - 1]);
+
+        // check if character is letter
+        if (isalpha(inputChar))
+        {
+            inputString[pos++] = tolower(inputChar);
+            continue;
+        }
+
+        // check if char is ' or - and if it is preceded by a letter
+        // eg yours-not, persons' (valid)
+        if ((inputChar == '\'' || inputChar == '-') && isPrevCharAlpha)
+        {
+            inputString[pos++] = inputChar;
+            continue;
+        }
+
+        // making sure that there is something valid in inputString
+        if (pos == 0)
+            continue;
+
+        // if last character is not letter and is not ' then replace by \0
+        if (!isPrevCharAlpha && inputString[pos - 1] != '\'')
+            pos--;
+        inputString[pos] = '\0';
+        pos = 0;
+        isPrevCharAlpha = false;
+        root = addWordToTree(inputString, root);
+    }
+    // this is to catch the case for the EOF
+    // being immediately after the last letter or '
+    if (pos > 0)
+    {
+        if (!isPrevCharAlpha && inputString[pos - 1] != '\'')
+            pos--;
+        inputString[pos] = '\0';
+        root = addWordToTree(inputString, root);
+    }
+
+    free(inputString);
+    return root;
+}
+
+/**
+ * Adding words in to the correct position in the tree
+ * @param word word to be inserted in to the tree
+ * @param currentNode current node of the tree which we comparing against
+ */
+struct Node *addWordToTree(char *word, struct Node *currentNode)
+{
+    if (currentNode == NULL)
+    {
+        struct Node *currentNode = allocateMemoryForNode();
+        currentNode->word = getPointerToWord(word);
+        currentNode->frequency = 1;
+        currentNode->left = NULL;
+        currentNode->right = NULL;
+        return currentNode;
+    }
+    int compared = strcmp(word, currentNode->word);
+
+    if (compared > 0)
+        currentNode->right = addWordToTree(word, currentNode->right);
+    else if (compared < 0)
+        currentNode->left = addWordToTree(word, currentNode->left);
+    else
+    {
+        currentNode->frequency++;
+    }
+    return currentNode;
+}
+
+/**
+ * Writes contents of the tree to another file alphabetically
+ * @param node current node to be printed to file
+ * @param file pointer to file to be written to
+ */
+void writeContentOfTreeToFile(struct Node *node, FILE *file)
+{
+    static int i = 1;
+    if (node != NULL)
+    {
+        writeContentOfTreeToFile(node->left, file);
+        fprintf(file, "%-5d \t %-9u \t %s \n", i++, node->frequency,
+                node->word);
+        writeContentOfTreeToFile(node->right, file);
+    }
+}
+
+/**
+ * Stores a word and returns address to memory
+ * @param word word to be stored in memory
+ */
+char *getPointerToWord(char *word)
+{
+    char *string = (char *)malloc((strlen(word) + 1) * sizeof(char));
+    // + 1 is for the '\0' character
+    if (string != NULL)
+    {
+        strcpy(string, word);
+        return string;
+    }
+    endProgramAbruptly(
+        "\n A problem occurred while reserving memory for word \n");
+    return NULL;
+}
+
+/**
+ * Reserves memory capable of storing a node and returns the address
+ */
+struct Node *allocateMemoryForNode()
+{
+    struct Node *node = (struct Node *)malloc(sizeof(struct Node));
+    if (node != NULL)
+        return node;
+    endProgramAbruptly(
+        "\n A problem occured while reserving memory for structure \n");
+    return NULL;
+}
+
+/**
+ * Closes a file when the read or write process is done
+ * @param file pointer to file to be closed
+ */
+void closeFile(FILE *file)
+{
+    int closed = fclose(file);
+    if (closed != 0)
+        endProgramAbruptly(" \n A Problem Occurred while closing a file \n");
+}
+
+/**
+ * Freeing memory when program is terminating
+ * @param node pointer to node to free
+ */
+void freeTreeMemory(struct Node *node)
+{
+    if (node != NULL)
+    {
+        freeTreeMemory(node->left);
+        freeTreeMemory(node->right);
+        free(node->word);
+        // freeing node->word because memory was allocated using malloc
+        free(node);
+        // freeing node because memory was allocated using malloc
+    }
+}
+
+/**
+ * Ending the program due to an error
+ * @param errorMessage This is the error message to be printed
+ */
+void endProgramAbruptly(char *errorMessage)
+{
+    fprintf(stderr, "%s\n", errorMessage);
+    exit(EXIT_FAILURE);
+}