# Travesal of Binary Tree

by Traversal of the binary tree

A node is visited only once in the traversal of the binary tree. There are three main types of traversal methods in the binary tree.

1. In-order traversal
2. Pre-order traversal
3. Post-order traversal

In-order traversal:

In the in-order traversal method, the left child and left subtree are traversed first, afterward the root tree and then the right children or the right subtree are traversed.

Algorithm of In-order traversal

 In-order-traversal (tree) Step 1: Start with left sub-tree        // call In-order (left subtree) Step 2: Then, root tree Step 3: And then, right sub-tree    // call In-order (right subtree)

Example: Find the in-order traversal for this tree.

 Solution.                            Step 1: Left sub-tree is 1 → 4 → 9 Step 2: Root node is 5 Step 3: Right sub-tree is 5 → 7 → 2 → 6 → 3    In-order Traversal = 1 → 4 → 9 → 5 → 5 → 7 → 2 → 6 → 3

Pre-order Traversal:

In the pre-order traversal method, the root node is traversed first, then the left subtree, and then the right subtree is traversed.

Algorithm of pre-order traversal

 Pre-order-traversal (tree) Step 1: Start with the root node    Step 2: Then, the left sub-tree       // call Pre-order (left subtree) Step 3: And then, right sub-tree    // call Pre-order (right subtree)

Example: Find the pre-order traversal for this tree.

 Solution.                            Step 1: Root node is 5 Step 2: Left sub-tree is 4 → 1 → 9 Step 3: Right sub-tree is 6 → 7 → 5 → 2 → 3    Pre-order Traversal = 5 → 4 → 1 → 9 → 6 → 7 → 5 → 2 → 3

Post-order traversal:

In the post-order traversal method, the left child and left subtree are traversed first, then the right subtree is traversed, and then the root node.

Algorithm of Post-order traversal

 Post-order-traversal (tree) Step 1: Start with left sub-tree        // call Post-order (left subtree) Step 2: Then, right sub-tree           // call Post-order (right subtree) Step 3: And then, root tree

Example: Find the Post-order traversal for this tree.

 Solution.                            Step 1: Left sub-tree is 1 → 9 → 4 Step 2: Right sub-tree is 5 → 2 → 7 → 3 → 6 Step 3: Root node is 5    Post-order Traversal = 1 → 9 → 4 → 5 → 2 → 7 → 3 → 6 → 5

Applications of binary tree

1. The binary search tree is used in many search applications.
2. Nowadays, a binary Space Partition is used for every 3D game.3.
3. The binary tree is used in every high bandwidth router that stores the router table.

### Binary tree program in C language

 // Binary Tree in C   #include #include   struct node {   int data;   struct node *left;   struct node *right; }; struct node *newNode(int data) {   struct node *node = (struct node *)malloc(sizeof(struct node));   node->data = data;   node->left = NULL;   node->right = NULL;   return (node); }   void traversePreOrder(struct node *t) {   if (t != NULL)   {     printf(” %d”, t->data);     traversePreOrder(t->left);     traversePreOrder(t->right);   } }   void traverseInOrder(struct node *t) {   if (t != NULL)   {     traverseInOrder(t->left);     printf(” %d”, t->data);     traverseInOrder(t->right);   } }   void traversePostOrder(struct node *t) {   if (t != NULL)   {     traversePostOrder(t->left);     traversePostOrder(t->right);     printf(” %d”, t->data);   } }   int main() {   struct node *root = newNode(1);   root->left = newNode(2);   root->right = newNode(3);   root->left->left = newNode(4);   printf(“The preorder traversal of the tree is: “);   traversePreOrder(root);   printf(“\nThe inorder traversal of the tree is: “);   traverseInOrder(root);   printf(“\nThe postorder traversal of the tree is: “);   traversePostOrder(root); }
by 