Chapter 6, Problem 20E

Explanation of Solution

Employing the functions to complete the Example 6.73:

• The Example 6.73 explains about imitating the iterators in C.
• In that example, they decouple the enumeration of a collection from original use of elements by taking appropriate programming conventions.
• There are two differences between the codes.
• 1. ○ The syntax of the loop is good and elegant.
  2. ○ The iterator is simply a type and some associated functions, C gives no abstraction technique to group them together as a class.
• The following program expands the Example 6.73 with the code for “tree_iter type (struct)” and “ti_create”, “ti_done”, “ti_next”, “ti_val”, and “ti_delete” functions.

Program:

//Defining structure to the tree node

typedef struct tree_node

{

    //Defining the value in data

    data val;

    //Defining left and right node using pointers

    struct tree_node *left, *right;

} tree_node;

/* a tree_iter contains a list-based stack of

tree_nodes (subtrees) that have yet to be visited */

//Defining the structure for list_ node

typedef struct list_node

{

    //Defining the tree_node

    tree_node *tn;

    //Defining the list_node

    struct list_node *next;

} list_node;

//Defining the structure for list_node and tree_iter

typedef list_node *tree_iter;

/*Defining the push method which push the element to the stack based on pointers*/

void ti_push(tree_node *n, tree_iter *tp)

{

    if (n)

    {

        list_node *t = *tp;

        *tp = (tree_iter) malloc(sizeof(list_node));

        (*tp)->tn = n; (*tp)->next = t;

    }

}

/* Creating the tree with tree_node and tree_iter creates assigns 0 to push element*/

void ti_create(tree_node *root, tree_iter *tp)

{

    *tp = 0;

    ti_push(root, tp);

}

//If adding the element to list is finished, it retruns the ti...