Level order traversal using queue in scala
Scala program for Level order traversal using queue. Here more information.
/*
Scala program for
Level order tree traversal using queue
*/
// Create Q node
class QNode(var data: TreeNode,
var next: QNode)
{
def this(node: TreeNode)
{
this(node, null);
}
}
// Binary Tree Node
class TreeNode(var data: Int,
var left: TreeNode,
var right: TreeNode)
{
def this(data: Int)
{
// Set node value
this(data, null, null);
}
}
class MyQueue(var head: QNode,
var tail: QNode,
var count: Int)
{
def this()
{
this(null, null, 0)
}
def size(): Int = {
return this.count;
}
def isEmpty(): Boolean = {
return this.count == 0;
}
// Add new node of queue
def enqueue(value: TreeNode): Unit = {
// Create a new node
var node: QNode = new QNode(value);
if (this.head == null)
{
// Add first element into queue
this.head = node;
}
else
{
// Add node at the end using tail
this.tail.next = node;
}
this.count += 1;
this.tail = node;
}
// Delete a element into queue
def dequeue(): Unit = {
if (this.head == null)
{
// Empty Queue
return;
}
// Visit next node
this.head = head.next;
this.count -= 1;
if (this.head == null)
{
// When deleting a last node of linked list
this.tail = null;
}
}
// Get front node
def peek(): TreeNode = {
if (this.head == null)
{
return null;
}
return this.head.data;
}
}
class BinaryTree(var root: TreeNode)
{
def this()
{
this(null)
}
def levelOrder(): Unit = {
if (this.root != null)
{
var q: MyQueue = new MyQueue();
// Add first node
q.enqueue(this.root);
var node: TreeNode = this.root;
while (q.isEmpty() == false && node != null)
{
if (node.left != null)
{
// Add left child node
q.enqueue(node.left);
}
if (node.right != null)
{
// Add right child node
q.enqueue(node.right);
}
// Display level node
print(" " + node.data);
// Remove current node
q.dequeue();
// Get new head
node = q.peek();
}
}
else
{
println("Empty Tree");
}
}
}
object Main
{
def main(args: Array[String]): Unit = {
// Create new tree
var tree: BinaryTree = new BinaryTree();
/*
Make A Binary Tree
-----------------------
1
/ \
2 3
/ / \
4 5 6
/ / \
7 8 9
*/
// Adding tree nodes
tree.root = new TreeNode(1);
tree.root.left = new TreeNode(2);
tree.root.right = new TreeNode(3);
tree.root.right.right = new TreeNode(6);
tree.root.right.left = new TreeNode(5);
tree.root.left.left = new TreeNode(4);
tree.root.left.left.left = new TreeNode(7);
tree.root.right.left.left = new TreeNode(8);
tree.root.right.left.right = new TreeNode(9);
// Display level order element
tree.levelOrder();
}
}
Output
1 2 3 4 5 6 7 8 9
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