1. ECE 103 Engineering Programming Chapter 64 Tree Implementation
Herbert G. Mayer, PSU CS
Status 6/4/2014
Initial content copied verbatim from
ECE 103 material developed by
Professor Phillip PSU ECE

2. Syllabus
Pointer Version

3. Tree : Pointer Version
A binary sort tree is created using pointers to nodes.
Nodes are created at runtime using malloc(). 2

4. Define structure of tree element
struct tree_node {
int value; /* Node value */
struct tree_node *left; /* Pointer to left child node */
struct tree_node *right; /* Pointer to right child node */ };
typedef struct tree_node Node; 3

5. Binary sort tree 4 tree value left right value left … right value left

6. Create the tree 5 int main (void) {
Node *tree = NULL; /* Pointer to tree */
int rvalue; /* Random value */
int k; /* Loop index */
srand(time(NULL)); /* Initialize random seed */
/* Build the tree with randomly generated values */
printf("Original values: ");
for (k = 0; k < 10; k++)
rvalue = rand() % ; /* 1 to 100 */
printf("%d ", rvalue);
insert_node(&tree, rvalue); }
/* Show sorted list of values */
printf("\n\nSorted values: ");
display_inorder(tree);
return 0; 5

7. Create a new tree node 6 Node * create_node (int num) {
Node *p; /* Work pointer */
/* Use run-time memory allocation to create new node */
if ((p = (Node *) malloc(sizeof(Node))) == NULL)
printf("ERROR: Unable to allocate memory for node\n");
exit(1); }
/* Initialize contents of new node */
p->value = num;
p->left = NULL;
p->right = NULL;
return p; /* Return pointer to newly created node */ 6

8. Insert a new node in the tree
void insert_node (Node **tree, int value) {
/* The value is sorted as it is placed in the binary tree */
if (*tree == NULL)
/* No more children, so insert here */
*tree = create_node(value);
else if (value <= (*tree)->value)
/* Traverse left branch */
insert_node(&(*tree)->left, value);
else
/* Traverse right branch */
insert_node(&(*tree)->right, value); } 7

9. Display the contents of the entire tree
void display_inorder (Node *tree) {
/* Use inorder recursion */
if (tree->left != NULL)
display_inorder(tree->left);
printf("%d ", tree->value);
if (tree->right != NULL)
display_inorder(tree->right); } 8

10. Example: 9 Pre-order traversal: display node traverse(left)
traverse(right)
Display order:
In-order traversal:
Post-order traversal:
Sample binary tree 8 6 79 64 86 56 39 13 46 42
tree
Original order of input values: 9