Trees - Data Structure || Implementation & PreOrder PostOrder and InOrder Traversal

 Tree  - means root, parent and child nodes, leaf nodes

Root - at the top of the Tree
Internal  Nodes - parent and child
Leaf - Nodes at the end of the tree 

Binary  Tree - At most 0,1, 2 child nodes.
Full Binary Tree/Strict Binary Tree - 0 or 2 Children.
ACBT Almost Complete Binary Tree :
    1. Complete the tree with Left to Right 
    2. Complete the tree with level

Complete Binary Tee :  Except children at leaf every level needs to filled with children

Binary Search Tree:  height = log(n)

Inserted Left element are need to smaller and Right element need to greater.

How to insert and traverse the Binary search tree:

Right side nodes will be greater than root
Left side nodes will be less than root


Pre Order, In Order, Post Order:

InOrder  - Left Root Right
PreOrder - Root Left Right
Post Order - Left Right Root

import java.util.Scanner;

class tree {

    static Scanner sc = new Scanner(System.in);

    public static void main(String args[]) {

        Node root = createTree();

        inOrder(root);

        System.out.println();

        preOrder(root);

        System.out.println();

        postOrder(root);

    }

    static Node createTree() {

        Node root = null;

        System.out.println("Enter the data");

        int data = sc.nextInt();

        if (data == -1) {

            return null;

        }

        root = new Node(data);

        System.out.println("Enter the left " + data);

        root.left = createTree();

        System.out.println("Enter the right" + data);

        root.right = createTree();

        return root;

    }

    static void inOrder(Node root) {

        if (root == null) {

            return;

        }

        inOrder(root.left);

        System.out.print(root.data + " ");

        inOrder(root.right);

    }

    static void preOrder(Node root) {

        if (root == null) {

            return;

        }

        System.out.print(root.data + " ");

        preOrder(root.left);

        preOrder(root.right);

    }

    static void postOrder(Node root) {

        if (root == null) {

            return;

        }

        postOrder(root.left);

        postOrder(root.right);

        System.out.print(root.data + " ");

    }

}

class Node {

    Node left;

    Node right;

    int data;

    Node(int d) {

        this.data = d;

    }

}

 Input :

2 4 7 -1 -1 -1 1 8 -1 -1 3 -1 -1 

Output:

Video Reference:

Anuj Bhaiya : 

Implementation : https://www.youtube.com/watch?v=QhIM-G7FAow
Traversal Techniques : https://www.youtube.com/watch?v=cFRRgwPIk2s