I am trying to delete the largest node in binary search tree, I thougth that these code below should be able to do it but for some reason it is not. Could someone help please!
public void remove() {
Node current = root;
while(true){
Node parent = current;
current = current.getRighChild();
if (current == null){
parent.setRighChild(null);
return;
}
}
}
public void remove()
{
root = deleteMax(root);
}
private Node deleteMax(Node x ) {
if (x.getRighChild() == null)
{
return x.getLeftChild();
}
x.setRighChild(deleteMax(x.getRighChild()));
return x;
}
In your code if the right node is empty you are still deleting it. Instead of deleting the current if it is the max. Try something like this:
removeLargest() {
current = getRoot();
rightNode == null;
while (root.Right){
current == root.Right
}
if (current.left()){
rotate()
}
current.delete()
}
Related
my assignment involves using recursive method. Write a program that reverses a LinkedList. This is the code i have done below, can anyone see what i am doing wrong, thank you very much!
PS: this is done in jGRASP
// Java program for reversing the linked list
class MyLinkedList {
static Node head;
static class Node {
int data;
Node next;
Node(int d) {
data = d;
next = null;
}
}
/* Function to reverse the linked list */
Node reverse(Node node) {
Node prev = null;
Node current = node;
Node next = null;
while (current != null) {
next = current.next;
current.next = prev;
prev = current;
current = next;
}
node = prev;
return node;
}
// prints content of double linked list
void printList(Node node) {
while (node != null) {
System.out.print(node.data + " ");
node = node.next;
}
}
public static void main(String[] args) {
MyLinkedList list = new MyLinkedList();
list.head = new Node(85);
list.head.next = new Node(15);
list.head.next.next = new Node(4);
list.head.next.next.next = new Node(20);
System.out.println("Given Linked list");
list.printList(head);
head = list.reverse(head);
System.out.println("");
System.out.println("Reversed linked list ");
list.printList(head);
}
}
I'm working with a treeview, which contains several columns, also one displaying a pixbuf, if audio is playing or paused. If the user double clicks on one row, audio playback starts and the row needs to be rerendered in order to display the pixbuf icon. I used QueueDraw for this, but that does only work, if the cursor leaves the current row. How can I update the pixbuf directly?
CODE:
protected void trvMainCuesheetRowActivated (object o, RowActivatedArgs args)
{
log.debug("trvMainCuesheetRowActivated called");
TreeIter ti = TreeIter.Zero;
this.lsCuesheetData.GetIter(out ti,args.Path);
if (this.lsCuesheetData.GetValue(ti,0) != null)
{
Track tCurTrack = (Track)this.lsCuesheetData.GetValue(ti,0);
if (this.objProgram.getAudioManager().getPlayState() == AudioCuesheetEditor.AudioBackend.PlayState.Stopped)
{
this.objProgram.getAudioManager().play(tCurTrack);
this.refresh();
}
else
{
if (this.objProgram.getAudioManager().getPlayState() == AudioCuesheetEditor.AudioBackend.PlayState.Playing)
{
this.objProgram.getAudioManager().seek(tCurTrack);
this.refresh();
}
}
}
}
private void renderPlaying(TreeViewColumn _tvcColumn, CellRenderer _crCell, TreeModel _tmModel, TreeIter _tiIter)
{
Track tCurTrack = (Track)_tmModel.GetValue (_tiIter, 0);
//Just display an icon, if we are playing
if (this.objProgram.getAudioManager().getPlayState() == AudioCuesheetEditor.AudioBackend.PlayState.Playing)
{
if (this.objProgram.getAudioManager().getCurrentlyPlayingTrack() == tCurTrack)
{
Gdk.Pixbuf icon = this.RenderIcon(Stock.MediaPlay, IconSize.SmallToolbar, null);
(_crCell as CellRendererPixbuf).Pixbuf = icon;
}
else
{
(_crCell as CellRendererPixbuf).Pixbuf = null;
}
}
else
{
if (this.objProgram.getAudioManager().getPlayState() == AudioCuesheetEditor.AudioBackend.PlayState.Paused)
{
if (this.objProgram.getAudioManager().getCurrentlyPlayingTrack() == tCurTrack)
{
Gdk.Pixbuf icon = this.RenderIcon(Stock.MediaPause, IconSize.SmallToolbar, null);
(_crCell as CellRendererPixbuf).Pixbuf = icon;
}
else
{
(_crCell as CellRendererPixbuf).Pixbuf = null;
}
}
else
{
(_crCell as CellRendererPixbuf).Pixbuf = null;
}
}
}
//Purpose: Function used to refresh the MainWindow depending on new options set.
public void refresh()
{
//QueueDraw is needed since it fires a signal to cellrenderers to update
this.trvMainCuesheet.QueueDraw();
this.sbMainWindow.Visible = this.objProgram.getObjOption().getBShowStatusbar();
this.mwToolbar.Visible = this.objProgram.getObjOption().getBToolbarVisible();
}
Greetings
Sven
Found the error myself.
this.objProgram.getAudioManager().getCurrentlyPlayingTrack()
didn't always return a track, where I expected one, so the renderer worked right. Bug is fixed, thanks anyway ;).
This is not an homework. I am just totally blocked on this. I know what to do but I am having difficulty manipulating the tree. please help.
I am trying to delete and node from an BST. I am able to lookup and find the parent and store it an tree.
package com.test.binarytree;
public class BinaryTreeDelete {
private Node root;
//create null binary tree
public BinaryTreeDelete(){
root = null;
}
//delete
public void delete(int target){
root = delete(root, target);
}
public Node delete(Node node, int target){
NodeWithParent temp = lookupFindParent(root, null, target);
if( node == null){
return null;
}
else{
if( node.left == null || node.right == null) //leaf node
{
//WHAT DO I DO HERE
//temp.parent.left = null;
//temp.parent.right = null;
//return null;
}
if( node.left != null && node.right == null ) //one child only on left
{
//WHAT DO I DO HERE
}
if( node.right != null && node.left == null ) //one child only on right
{
//WHAT DO I DO HERE
}
if( node.left != null && node.right != null ) //two children
{
//WHAT DO I DO HERE
}
}
return null;
}
private NodeWithParent lookupFindParent(Node node, Node parentNode, int target){
if( node == null ){
return null;
}
if( node.data == target){
return new NodeWithParent(node, parentNode);
}
else if( node.data > target ){
parentNode = node;
return lookupFindParent(node.left, parentNode, target);
}
else{
parentNode = node;
return lookupFindParent(node.right, parentNode, target);
}
}
//insert
public void insert(int data){
root = insert(root, data);
}
public Node insert (Node node, int data){
if(node == null){
node = new Node(data);
}
else{
if( data <= node.data ){
node.left = insert(node.left, data);
}
else{
node.right = insert(node.right, data);
}
}
return node;
}
//print tree
public void printTree(){
printTree(root);
System.out.println();
}
//print tree
private void printTree(Node node) {
if (node == null) return;
// left, node itself, right
printTree(node.left);
System.out.print(node.data + " ");
printTree(node.right);
}
//node class
public static class Node{
Node left;
Node right;
int data;
Node(int newNode){
data = newNode;
left = null;
right = null;
}
}
//node class
public static class NodeWithParent{
Node current;
Node parent;
NodeWithParent(Node current, Node parent){
this.current = current;
this.parent = parent;
}
}
public static void main(String[] args) {
BinaryTreeDelete bt = new BinaryTreeDelete();
//insert with inserts - tree increases on right if inserted in order
bt = new BinaryTreeDelete();
bt.insert(5);
bt.insert(3);
bt.insert(7);
bt.insert(1);
bt.insert(4);
bt.insert(6);
bt.insert(9);
bt.printTree();
//bt.delete(3);
//bt.delete(4);
//bt.delete(6);
bt.delete(9);
//bt.delete(5);
bt.printTree();
}
}
I'm going to provide you the logic (that means you have to write the code yourself) of how to delete a node in a BST.
There are three cases.
Node to be deleted has both left and right child as null: Delete the node and make the parent point to null.
Node to be deleted has either left or right child (but not both) as null: Delete the node but make sure that the parent points to the valid child of the to-be-deleted node.
Node to be deleted has nether left child nor right child as null: In this case, you have to find the next greater element of the to-be-deleted node. This next greater element is the least element of the right subtree of the to-be-deleted node. Since this is the least element, it has at least one of its child as null. So swap the values of the to-be-deleted node with the next greater node. After you swap, delete this next greater node using points 1 and 2 (whichever is fitting to the situation). Now, why the next greater node and not any node. Because if you replace a node with its next greater node, the BST remains a BST. Try it out in an example and it will be clear.
I have been sitting on this one for some time. In the Binary Search Tree, when you do a breadth first traversal There is this one line of code that I dont know what it does. In the textbook I am using the code is as follows.
public void breadthFirst()
{
BSTNode<T> p = root;
Queue<BSTNode<T>> queue = new Queue<BSTNode<T>>();
if(p != null)
{
queue.enqueue(p);
while(!queue.isEmpty())
{
**p = queue.dequeue();**
visit(p);
if(p.left != null)
{
queue.enqueue(p.left);
}
if(p.right != null)
{
queue.enqueue(p.right);
}
}
}
}
The Queue contains nodes that we have to visit. Before when we visit a node we take it out of the queue (dequeue) so that it will not be visited again.
This is a recursive method for finding the height, but i have a very large number of nodes in my binary search tree, and i want to find the height of the tree as well as assign the height to each individual sub-tree. So the recursive method throws stackoverflow exception, how do i do this non-recursively and without using stack?
private int FindHeight(TreeNode node)
{
if (node == null)
{
return -1;
}
else
{
node.Height = 1 + Math.Max(FindHeight(node.Left), FindHeight(node.Right));
return node.Height;
}
}
I believe i have to use post order traversal but without stack?
I was able to make this method, and it does return the correct height but it assigns each node with its depth not height.
public void FindHeight()
{
int maxHeight = 0;
Queue<TreeNode> Q = new Queue<TreeNode>();
TreeNode node;
Q.Enqueue(Root);
while (Q.Count != 0)
{
node = Q.Dequeue();
int nodeHeight = node.Height;
if (node.Left != null)
{
node.Left.Height = nodeHeight + 1;
Q.Enqueue(node.Left);
}
if (node.Right != null)
{
node.Right.Height = nodeHeight + 1;
Q.Enqueue(node.Right);
}
if (nodeHeight > maxHeight)
{
maxHeight = nodeHeight;
}
}
Console.WriteLine(maxHeight);
}