**Tree** :Binary Tree is a special data structure used for data storage purposes. A binary tree has a special condition that each node can have a maximum of two children.

A** complete binary tree** is a tree, which is completely filled, with the possible exception of the bottom level, which is filled from left to right. A complete binary tree of the height h has between 2h and 2(h+1)-1

**Path −** Path refers to the sequence of nodes along the edges of a tree.

**Root −** The node at the top of the tree is called root. There is only one root per tree and one path from the root node to any node.

**Parent −** Any node except the root node has one edge upward to a node called parent.

**Child −** The node below a given node connected by its edge downward is called its child node.

**Leaf −** The node which does not have any child node is called the leaf node.

**Subtree −** Subtree represents the descendants of a node.

**Visiting −** Visiting refers to checking the value of a node when control is on the node.

**Traversing −** Traversing means passing through nodes in a specific order.

**Levels −** Level of a node represents the generation of a node. If the root node is at level 0, then its next child node is at level 1, its grandchild is at level 2, and so on.

**keys −** Key represents a value of a node based on which a search operation is to be carried out for a node.

**Binary search tree data structure,**

**Insert −** Inserts an element in a tree/create a tree.

**Search −** Searches an element in a tree.

**Preorder Traversal −** Traverses a tree in a pre-order manner.

**Inorder Traversal −** Traverses a tree in an in-order manner.

**Postorder Traversal −** Traverses a tree in a post-order manner.

**In-Order Display in Tree **

void inorder_traversal(node* root) { if (root != NULL) { inorder_traversal(root->leftChild); cout << root->data << " "; inorder_traversal(root->rightChild); } }

**Pre-order Display in Tree**

void pre_order_traversal(node* root) { if (root != NULL) { cout << root->data << " "; pre_order_traversal(root->leftChild); pre_order_traversal(root->rightChild); } }

**Post-Order Display in tree**

void post_order_traversal(node* root) { if (root != NULL) { post_order_traversal(root->leftChild); post_order_traversal(root->rightChild); cout << root->data << " "; }