Algorithms/JavaAlgorithms
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Merge pull request #103 from mpokryva/level-order

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Added level order traversal, and more nodes in main method
This commit is contained in:
Chetan Kaushik 2017-10-18 22:44:13 +05:30 committed by GitHub
commit ef1aa79bd5
1 changed files with 40 additions and 32 deletions
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52
data_structures/Trees/TreeTraversal.java
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@ -1,33 +1,37 @@
import java.util.LinkedList;
/** /**
* *
* @author Varun Upadhyay (https://github.com/varunu28) * @author Varun Upadhyay (https://github.com/varunu28)
* *
*/ */
import java.util.LinkedList;
// Driver Program // Driver Program
public class TreeTraversal { public class TreeTraversal {
public static void main(String[] args) { public static void main(String[] args) {
Node tree = new Node(5); Node tree = new Node(5);
tree.insert(3); tree.insert(3);
tree.insert(2);
tree.insert(7); tree.insert(7);
tree.insert(1); tree.insert(4);
tree.insert(9); tree.insert(6);
tree.insert(8);
// Prints 1 3 5 7 9 // Prints 5 3 2 4 7 6 8
tree.printInOrder(); System.out.println("Pre order traversal:");
System.out.println();
// Prints 5 3 1 7 9
tree.printPreOrder(); tree.printPreOrder();
System.out.println(); System.out.println();
// Prints 2 3 4 5 6 7 8
// Prints 1 3 9 7 5 System.out.println("In order traversal:");
tree.printInOrder();
System.out.println();
// Prints 2 4 3 6 8 7 5
System.out.println("Post order traversal:");
tree.printPostOrder(); tree.printPostOrder();
System.out.println(); System.out.println();
// Prints 5 3 7 2 4 6 8
// Add a couple more nodes for print level test System.out.println("Level order traversal:");
// Print 5 3 7 1 9
tree.printLevelOrder(); tree.printLevelOrder();
System.out.println(); System.out.println();
} }
@ -39,7 +43,7 @@ public class TreeTraversal {
* printInOrder: LEFT -> ROOT -> RIGHT * printInOrder: LEFT -> ROOT -> RIGHT
* printPreOrder: ROOT -> LEFT -> RIGHT * printPreOrder: ROOT -> LEFT -> RIGHT
* printPostOrder: LEFT -> RIGHT -> ROOT * printPostOrder: LEFT -> RIGHT -> ROOT
* printLevelOrder: ROOT -> ROOT's CHILDREN -> ROOT's CHILDREN's CHILDREN -> etc * printLevelOrder: Prints by level (starting at root), from left to right.
*/ */
class Node { class Node {
Node left, right; Node left, right;
@ -98,19 +102,23 @@ class Node {
System.out.print(data + " "); System.out.print(data + " ");
} }
/**
* O(n) time algorithm.
* Uses O(n) space to store nodes in a queue to aid in traversal.
*/
public void printLevelOrder() { public void printLevelOrder() {
LinkedList<Node> queue = new LinkedList<>(); LinkedList<Node> queue = new LinkedList<>();
queue.add(this); queue.add(this);
while(!queue.isEmpty()) { while (queue.size() > 0) {
Node n = queue.poll(); Node head = queue.remove();
System.out.print(n.data + " "); System.out.print(head.data + " ");
if (n.left != null) { // Add children of recently-printed node to queue, if they exist.
queue.add(n.left); if (head.left != null) {
queue.add(head.left);
} }
if (n.right != null) { if (head.right != null) {
queue.add(n.right); queue.add(head.right);
} }
} }
} }
} }