122 lines
3.1 KiB
Java
122 lines
3.1 KiB
Java
package DataStructures.Trees;
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import java.util.LinkedList;
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/**
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* @author Varun Upadhyay (https://github.com/varunu28)
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*/
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// Driver Program
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public class TreeTraversal {
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public static void main(String[] args) {
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Node tree = new Node(5);
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tree.insert(3);
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tree.insert(2);
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tree.insert(7);
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tree.insert(4);
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tree.insert(6);
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tree.insert(8);
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// Prints 5 3 2 4 7 6 8
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System.out.println("Pre order traversal:");
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tree.printPreOrder();
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System.out.println();
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// Prints 2 3 4 5 6 7 8
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System.out.println("In order traversal:");
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tree.printInOrder();
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System.out.println();
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// Prints 2 4 3 6 8 7 5
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System.out.println("Post order traversal:");
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tree.printPostOrder();
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System.out.println();
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// Prints 5 3 7 2 4 6 8
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System.out.println("Level order traversal:");
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tree.printLevelOrder();
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System.out.println();
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}
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}
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/**
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* The Node class which initializes a Node of a tree
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* Consists of all 4 traversal methods: printInOrder, printPostOrder， printPreOrder & printLevelOrder
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* printInOrder: LEFT -> ROOT -> RIGHT
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* printPreOrder: ROOT -> LEFT -> RIGHT
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* printPostOrder: LEFT -> RIGHT -> ROOT
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* printLevelOrder: Prints by level (starting at root), from left to right.
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*/
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class Node {
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Node left, right;
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int data;
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public Node(int data) {
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this.data = data;
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}
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public void insert(int value) {
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if (value < data) {
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if (left == null) {
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left = new Node(value);
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} else {
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left.insert(value);
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}
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} else {
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if (right == null) {
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right = new Node(value);
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} else {
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right.insert(value);
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}
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}
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}
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public void printInOrder() {
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if (left != null) {
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left.printInOrder();
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}
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System.out.print(data + " ");
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if (right != null) {
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right.printInOrder();
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}
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}
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public void printPreOrder() {
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System.out.print(data + " ");
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if (left != null) {
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left.printPreOrder();
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}
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if (right != null) {
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right.printPreOrder();
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}
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}
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public void printPostOrder() {
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if (left != null) {
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left.printPostOrder();
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}
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if (right != null) {
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right.printPostOrder();
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}
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System.out.print(data + " ");
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}
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/**
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* O(n) time algorithm.
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* Uses O(n) space to store nodes in a queue to aid in traversal.
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*/
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public void printLevelOrder() {
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LinkedList<Node> queue = new LinkedList<>();
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queue.add(this);
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while (queue.size() > 0) {
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Node head = queue.remove();
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System.out.print(head.data + " ");
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// Add children of recently-printed node to queue, if they exist.
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if (head.left != null) {
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queue.add(head.left);
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}
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if (head.right != null) {
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queue.add(head.right);
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}
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}
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}
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}
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