I'm trying to convert a 2-3-4 Tree into a Red-Black tree in java, but am having trouble figuring it out.
I've written these two basic classes as follows, to make the problem straightforward, but can't figure out where to go from here.
public class TwoThreeFour<K> {
public List<K> keys;
public List<TwoThreeFour<K>> children;
}
public class RedBlack<K> {
public K key;
public boolean isBlack;
public RedBlack<K> left,right;
public RedBlack<K key, boolean isBlack, RedBlack<K> left, RedBlack<K> right){
this.key = key; this.isBlack = isBlack; this.left = left; this.right = right;
}
}
I'm assuming the 2-3-4 tree is valid, and want to return a red black tree when the method is called.
I've also tried the following code with no luck:
public convert(TwoThreeFour<K> tTF){
if (ttf.keys.size() == 3)
RedBlack<K> node = RedBlack<ttf.keys[1], true, RedBlack<ttf.keys[0], false, /* not sure what to put here for left */, /* not sure what to put here for right */), RedBlack<ttf.keys[2], false, /* not sure what to put here for left */, /* not sure what to put here for right */)
etc. for keys.size() == 2, 1....
I know it has to be recursive in theory, but am having a hard time figuring it out. Any thoughts?
Consider these three rules:
Transform any 2-node in the 2-3-4 tree into a black node in the
red-black tree.
Transform any 3-node into a child node and a parent node. The
child node has two children of its own: either W and X or X and Y.
The parent has one other child: either Y or W. It doesn’t matter
which item becomes the child and which the parent. The child is
colored red and the parent is colored black.
Transform any 4-node into a parent and two children, the first
child has its own children W and X; the second child has children Y
and Z. As before, the children are colored red and the parent is
black.
The red-black rules are automatically satisfied if you follow these rules. Here's the resulting example tree after applying the transformations.
Hopefully that should get you going. For easy to understand and detailed explanation, you can refer to Robert Lafore's Data Structures book.
Related
I have a graph with nodes to color, where for each node a dataset (a collection of rows / tuples) is associated.
The algorithm is explained by this example:
the uploaded figure shows an execution of Coloring over graph G with
nodes {v1, v3, v2}. Figure (a) initializes nodes as
uncolored. We first consider v1, and select Sσ1 = {{t9, t10}} (Figure (b)). We color nodes v2 and v3 by recursively calling Coloring.
Coloring one node may restrict the color choice of neighboring nodes,
e.g. after we select {{t9, t10}} for v1, we cannot select {{t6, t7,
t10}} for v3 due to the overlapping tuple t10. For node v3,
we have several choices including {{t6, t7}} and {{t7, t8}}. In Figure (c), we assume the coloring algorithm chooses {{t6, t7}} for
v3. As a result, {{t5, t6}}, which was the only choice forv2, cannot
be used due to the overlapping tuple t6. This leads the algorithm
towards an unsatisfying clustering (Figure (d)). The algorithm
backtracks its last decision for v3 by selecting a different color,
{{t7, t8}} for v3 in Figure (e). In this case, the clustering {{t5,
t6}} for v2 does not overlap with {{t7, t8}}. Since we have found a
clustering that satisfies all the constraints (i.e., a coloring of all nodes), Coloring returns true with V containing the nodes and their colors
(i.e., clusterings).
Here's my code i am trying (which i suspect it is wrong the way it colors the nodes because the algorithm runs for too long )
nodeIterator parameter contains all nodes of the graph sorted in customized way.
public Boolean coloring(graph, nodeIterator, vector){
Node nodeIt ;
if (nodeIterator.hasNext())
nodeIt = nodeIterator.next();
else {
return false;
}
// cluster is the current node associated dataset
ArrayList<Dataset<Row>> cluster = allClustersOfGraph.getNextDataset(nodeIt.name);
if (graph.getNeighbors(nodeIt) == null) {
if (!nodeIterator.hasNext()){
colorNode(vector, nodeIt);
return false;
}
else {
colorNode(vector, nodeIt);
nodeIterator.next();
}
}
Iterable<Node> adjNodes = graph.getNeighbors(nodeIt);
Iterator<Node> adjNodesIt = adjNodes.iterator();
// i suspect in the line under, while is an if so that next neighboring nodes of the current processed one, will be in turn processed in the next recursive call of this algorithm
while (adjNodesIt.hasNext()){
Node adjNode = adjNodesIt.next();
if (!checkNodeColored(vector, adjNode)) {
ArrayList<Dataset<Row>> adjCluster = allClustersOfGraph.getNextDataset(adjNode.name);
for (Dataset<Row> subCluster : cluster) {
for (Dataset<Row> subAdjCluster : adjCluster) {
// small datasets (tuples of rows) don't intersect
if (noDatasetIntersection(subCluster, subAdjCluster)) {
colorNode(vector, nodeIt, subCluster);
if (coloring(graph, nodeIterator, vector)) {
return true;
} else {
// vector is where current coloring progress is maintained
// move backwards
vector.remove(vector.size() - 1);
}
}
}
}
} else if (!adjNodesIt.hasNext()) {
// Color last node anyway
colorNode(vector, nodeIt);
return true;
}
}
return false;
}
allClustersOfGraph is of type ArrayList<ArrayList<Dataset<Row>>>
Here's also the pseudo-algorithm :
My question is : i created the loop while (adjNodesIt.hasNext()){...in my code to check for one recursive call all neighboring nodes of the current processed node, is it right to do that in a recursive method ? Also are all limit cases treated through my implementation ?
Thanks for the great help!
I'm working on building a partial tree for Monte Carlo Search Tree, I have my node class and it contains things like the game board, who's turn it is, and a list of Nodes for the children nodes. The node constructor takes in a game board and the depth (of the tree) as the parameters. For the root node I call it like so:
Node root = new Node(this.quartoBoard, currentDepth);
(Where depth is 0) that works fine, however, when depth 1, which will be the children of the root node needs to contain 32 nodes. I naively tried this:
for(int i = 0; i < NUMBER_OF_PIECES; i++) {
Node c1 = new Node(this.quartoBoard, currentDepth);
c1.setParent(root);
childrenList1.add(c1);
}
And realized that Nodes can not be created in a for loop like this. Is there an alternative to declaring each node one at a time like so:
Node child1 = new Node(this.quartoBoard, currentDepth);
Node child2 = new Node(this.quartoBoard, currentDepth);
I need to create over 800 nodes and I feel like there is a better way to do it, I just am drawing blanks on how. Any help is greatly appreciated!
So I'm trying to write a RR Rotation and LL Rotation with Java for an AVL tree. I have most of it figured out, however I don't know where I should modify the height within the method. I've been trying to understand it for a few days here but I cannot figure out where exactly it would go in the method I currently have. If someone could help explain exactly where I should put the modifications for the height of the node (it uses getLeft/setLeft for it's left height and getRight/setRight for it's right height) it would be extremely helpful!
/**
* Performs a right shift of the current critical node. (Left rotation)
* #precond Tree is not empty.
* #return a tree with the updated rotation.
**/
public BinaryNodeAVL280<I> shiftLeftRotation(BinaryNodeAVL280<I> critNode)
{
if(this.rootNode() == null)
{
throw new ContainerEmpty280Exception("Cannot rotate an empty AVL tree!");
}
//TempNode becomes right of A (which is C)
BinaryNodeAVL280<I> tempNode = (BinaryNodeAVL280<I>) critNode.rightNode();
//Set the parent of tempNode (A) to be critNode's parent.
tempNode.setParent(critNode.getParent());
//Set critNode (A)'s left Node (which is B) to tempNode's leftNode (C's left which is D)
critNode.setRightNode(tempNode.leftNode());
//Check if the rightNode of A is null.
if(critNode.rightNode() != null)
{
//If not null, set A's right parent (C's parent) to current parent.
((BinaryNodeAVL280<I>) critNode.rightNode()).setParent(critNode);
}
//Set Left node of C (was D) to critNode (A)
tempNode.setLeftNode(critNode);
//Set critNode's (unknown for now) to temp node (C).
critNode.setParent(tempNode);
//If parent of C is not null.
if(tempNode.getParent() != null)
{
//If the right child of tempNode is the same as critNode
if(tempNode.getParent().rightNode() == critNode)
//Set the right child to tempNode.
tempNode.getParent().setRightNode(tempNode);
//If the child of temp node's left side is equal to critNode
else if(tempNode.getParent().leftNode() == critNode)
//Set temp node's left to tempNode(b)
tempNode.getParent().setLeftNode(tempNode);
}
//increment height somehow...
return tempNode;
}
So, my issue is this: I'm attempting to define a custom set of nodes for a Javafx XYChart LineChart, where each node corresponds to a point that was plotted directly from the datasets. After looking around a little bit, Jewlesea actually had a solution at one point about how to add dynamic labels to nodes on a linechart graph that gave me enough of a push in the right direction to create black symbols (they are dots at the moment, but they can be many different things). Now I have a requirement that requires me to change ONE of the nodes on the XY chart into an 'X'. this could be either through loading an image in place of the 'node', or through physically manipulating the 'shape' parameter in .css.
The problem begins when I try to add this property dynamically, since which node has the 'x' will always be changing. Here are the things I've tried, and they all end up with no results whatsoever, regardless of the property used.
private XYChart.Data datum( Double x, Double y )
{
final XYChart.Data data = new XYChart.Data(x, y);
data.setNode(
new HoveredThresholdNode(x, y));
//data.getNode().setStyle("-fx-background-image: url(\"redX.png\");");
data.getNode().styleProperty().bind(
new SimpleStringProperty("-fx-background-color: #0181e2;")
.concat("-fx-font-size: 20px;")
.concat("-fx-background-radius: 0;")
.concat("-fx-background-insets: 0;")
.concat("-fx-shape: \"M2,0 L5,4 L8,0 L10,0 L10,2 L6,5 L10,8 L10,10 L8,10 L5,6 L2,10 L0,10 L0,8 L4,5 L0,2 L0,0 Z\";")
);
data.getNode().toFront();
return data;
}
So in the above, you can see that this is adding a property through the use of the 'bind' function after the dataNode has already been created. Also note above, I tried doing it through the 'setStyle' interface at this level to give it a background image, with no success. Also, no errors are being thrown, no 'invalid css' or anything of the sort, just simply no display on the graph at all when done this way.
now, in the HoveredThresholdNode (Again a big thanks to Jewelsea for being a master of Javafx and putting this bit of code online, it's where 90% of this class came from.) I tried essentially the same thing, at a different level. (actually being IN the node creation class, as opposed to a layer above it).
class HoveredThresholdNode extends StackPane {
/**
*
* #param x the x value of our node (this gets passed around a bunch)
* #param y the y value of our node (also gets passed around a bunch)
*/
HoveredThresholdNode(Double x, Double y) {
//The preferred size of each node of the graph
//getStylesheets().add(getClass().getResource("style/XYChart.css").toExternalForm());
//getStyleClass().add("xyChart-Node");
//setOpacity(.8);
styleProperty().bind(
new SimpleStringProperty("-fx-background-color: #0181e2;")
.concat("-fx-font-size: 20px;")
.concat("-fx-background-radius: 0;")
.concat("-fx-background-insets: 0;")
.concat("-fx-shape: \"M2,0 L5,4 L8,0 L10,0 L10,2 L6,5 L10,8 L10,10 L8,10 L5,6 L2,10 L0,10 L0,8 L4,5 L0,2 L0,0 Z\";")
);
//this label is the 'tooltip' label for the graph.
final Label label = createDataThresholdLabel(x, y);
final double Myx = x;
final double Myy = y;
setOnMouseEntered(new EventHandler<MouseEvent>() {
#Override public void handle(MouseEvent mouseEvent) {
if (Myx == 0) {
label.setTextFill(Color.DARKGRAY);
} else if (Myx > 0) {
label.setTextFill(Color.SPRINGGREEN);
} else {
label.setTextFill(Color.FIREBRICK);
}
label.setText("Current position: " + Myx + " , " + Myy);
//setCursor(Cursor.NONE);
toFront();
}
});
setOnMouseExited(new EventHandler<MouseEvent>() {
#Override public void handle(MouseEvent mouseEvent) {
//getChildren().clear();
//setCursor(Cursor.CROSSHAIR);
}
});
}
Now note, I also tried the setStyle(java.lang.String) method, with all of the same type of CSS, with no success. I have NO idea why this isn't styling dynamically. It's almost as if the custom nodes are simply ignoring all new .css that I define at runtime?
Any help would be greatly appreciated, please don't be shy if you need more details or explanation on any points.
So, I did finally find a good workaround to solve my problem, although not in the way I thought it would happen. The main problem I was having, was that I was extending from stackPane to create my node, which only had a very small number of graphical display options available to it, and by switching the 'prefSize()' property, I was simply changing the size of that stackPane, and then filling in the background area of that stack pane black, giving it a very deceptive shape-look to it.
So rather than use a stack pane, whenever I reached the node that I needed to place the red 'X' on, I simply called a different Datum method that returned a datum with an ImageView Attached, like so:
private XYChart.Data CoLDatum(Double x, Double y){
final XYChart.Data data = new XYChart.Data(x, y);
ImageView myImage = new ImageView(new Image(getClass().getResource("style/redX.png").toExternalForm()));
data.setNode(myImage);
data.getNode().setOnMouseEntered(new EventHandler<MouseEvent>() {
#Override public void handle(MouseEvent mouseEvent) {
main_label.setText("Some Text.");
}
});
data.getNode().setOnMouseExited(new EventHandler<MouseEvent>(){
#Override public void handle(MouseEvent mouseEvent) {
main_label.setText("");
}
});
return data;
}
and since ImageView is an implementing class of Node, this worked out just fine, and allowed me to load up an image for that one single node in the graph, while still maintaining a listener to give custom text to our information label when the red 'x' was hovered over with a mouse. Sometimes, it's the simple solutions that slip right past you.
I imagine that, had I employed stackPane properties properly with the setStyle(java.lang.String) method, they would have absolutely shown up, and I was just butchering the nature of a stack pane. Interesting.
Hopefully this helps somebody else stuck with similar problems!
I know this question has been asked before in a similar way, maybe for icons.
What I'm trying is to change the color of the text of the tree node.
In fact, I have a jTree and I will want to set up three differents colors, default one, red and orange.
The purposse, is that if I compare that tree with another one, highlight differences between both trees (default means no diff, orange means just value diff and red means node is complete different)
I have two functions, one which trasverse the "original" tree looking for a node from the compared one, and returns false if {node} is not found:
private Boolean findNodeInRefTree(DefaultTreeModel model, Object root, DefaultMutableTreeNode node){
Boolean bRet = false;
for (int i = 0; ((i < model.getChildCount(root))&&(!bRet)); i++){
DefaultMutableTreeNode child = (DefaultMutableTreeNode) model.getChild(root, i);
bRet = node.getUserObject().equals(child.getUserObject());
if (!bRet)
bRet = findNodeInRefTree(model, child, node);
}//for:i
return bRet;
}
And another function that trasverse the "compare" tree and calls the above for each node.
private void compareTrees(TreeModel model, Object root){
for (int i = 0; i < model.getChildCount(root); i++){
DefaultMutableTreeNode child = (DefaultMutableTreeNode) model.getChild(root, i);
//find if node exists in original
DefaultTreeModel modelRef = (DefaultTreeModel) _ref.getModel();
if (!findNodeInRefTree(modelRef, modelRef.getRoot(), child)){
DefaultTreeCellRenderer render = (DefaultTreeCellRenderer) _temp.getCellRenderer();
render.setForeground(Color.RED);
_temp.setCellRenderer(render);
}//fi
_new.insertNodeInto((DefaultMutableTreeNode) child, (DefaultMutableTreeNode) root, i);
compareTrees(model, child);
}//for:i
}
Then, when it ends I just set the model of the new tree {_new} to the new tree {_temp}, and add the tree to its panel. But the tree doesn't has any different color. Obviously, I'm testing with different trees. Any suggestion?
If I understand your code correctly, your do the comparison at creation time and set the renderer for each tree node (i.e. multiple times) inside method compareTrees.
Unfortunately, that is not the way tree renderers are handled in swing. The renderer is prepared on request during rendering the tree component. Thus setting multiple renderer beforehand won't do anything useful.
A possible approach would be to do the comparison and save the result (i.e. color) in your tree model. You can then write a basic tree renderer which reads this value for the current node and sets the rendering color accordingly.