1 files changed, 159 insertions, 0 deletions
diff --git a/reference/C/CONTRIB/OR_PRACTICAL_C/16_3.c b/reference/C/CONTRIB/OR_PRACTICAL_C/16_3.c
new file mode 100644
index 0000000..958e544
--- /dev/null
+++ b/reference/C/CONTRIB/OR_PRACTICAL_C/16_3.c
@@ -0,0 +1,159 @@
+/********************************************************
+ * words -- scan a file and print out a list of words   *
+ *              in ASCII order.                         *
+ *                                                      *
+ * Usage:                                               *
+ *      words <file>                                    *
+ ********************************************************/
+#include <stdio.h>
+#include <ctype.h>
+#include <string.h>
+#include <stdlib.h>     /* ANSI Standard only */
+
+struct node {
+    struct node    *right;      /* tree to the right */
+    struct node    *left;       /* tree to the left */
+    char           *word;       /* word for this tree */
+};
+
+/* the top of the tree */
+static struct node *root = NULL;
+
+main(int argc, char *argv[])
+{
+    void scan(char *);  /* scan the files for words */
+    void print_tree(struct node *);/* print the words in the file */
+
+    if (argc != 2) {
+        (void) fprintf(stderr, "Error:Wrong number of parameters\n");
+        (void) fprintf(stderr, "      on the command line\n");
+        (void) fprintf(stderr, "Usage is:\n");
+        (void) fprintf(stderr, "    words 'file'\n");
+        exit(8);
+    }
+    scan(argv[1]);
+    print_tree(root);
+    return (0);
+}
+/********************************************************
+ * 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 */
+
+    /* enter a word into the tree */
+    void enter(struct node **, char *);
+
+    in_file = fopen(name, "r");
+    if (in_file == NULL) {
+        (void) 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);
+    }
+    (void) fclose(in_file);
+}
+/********************************************************
+ * 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 */
+    void memory_error(void);    /* tell user no more room */
+
+    /* see if we have reached the end */
+    if ((*node) == NULL) {
+        (*node) = (struct node *) malloc(sizeof(struct node));
+        if ((*node) == NULL)
+            memory_error();
+        (*node)->left = NULL;
+        (*node)->right = NULL;
+        (*node)->word = save_string(word);
+    }
+    result = strcmp((*node)->word, word);
+    if (result == 0)
+        return;
+    if (result < 0)
+        enter(&(*node)->right, word);
+    else
+        enter(&(*node)->left, word);
+}
+/********************************************************
+ * 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();
+    (void) strcpy(new_string, string);
+    return (new_string);
+}
+/********************************************************
+ * memory_error -- write error and die                  *
+ ********************************************************/
+void memory_error(void)
+{
+    (void) fprintf(stderr, "Error:Out of memory\n");
+    exit(8);
+}
+/********************************************************
+ * 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);
+    (void) printf("%s\n", top->word);
+    print_tree(top->right);
+}