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package bjc.utils.funcdata.bst;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import java.util.function.Predicate;
import bjc.utils.funcdata.FunctionalList;
import bjc.utils.funcdata.ITreePart;
import bjc.utils.funcdata.ITreePart.TreeLinearizationMethod;
/**
* A binary search tree, with some mild support for functional traversal.
*
* @author ben
*
* @param <T>
* The data type stored in the node.
*/
public class BinarySearchTree<T> {
/**
* The comparator for use in ordering items
*/
private Comparator<T> comp;
/**
* The current count of elements in the tree
*/
private int nCount;
/**
* The root element of the tree
*/
private ITreePart<T> root;
/**
* Create a new tree using the specified way to compare elements.
*
* @param cmp
*/
public BinarySearchTree(Comparator<T> cmp) {
nCount = 0;
comp = cmp;
}
/**
* Add a node to the binary search tree.
*
* @param dat
* The data to add to the binary search tree.
*/
public void addNode(T dat) {
nCount++;
if (root == null) {
root = new BinarySearchTreeNode<T>(dat, null, null);
} else {
root.add(dat, comp);
}
}
/**
* Balance the tree, and remove soft-deleted nodes for free. Takes O(N)
* time, but also O(N) space.
*/
public void balance() {
FunctionalList<T> elms = new FunctionalList<>();
root.forEach(TreeLinearizationMethod.INORDER, e -> elms.add(e));
root = null;
int piv = elms.getSize() / 2;
int adj = 0;
while ((piv - adj) >= 0 && (piv + adj) < elms.getSize()) {
if (root == null) {
root = new BinarySearchTreeNode<T>(elms.getByIndex(piv), null, null);
} else {
root.add(elms.getByIndex(piv + adj), comp);
root.add(elms.getByIndex(piv - adj), comp);
}
adj++;
}
if ((piv - adj) >= 0) {
root.add(elms.getByIndex(piv - adj), comp);
} else if ((piv + adj) < elms.getSize()) {
root.add(elms.getByIndex(piv + adj), comp);
}
}
/**
* Soft-delete a node from the tree. Soft-deleted nodes stay in the
* tree until trim()/balance() is invoked, and are not included in
* traversals/finds.
*
* @param dat
*/
public void deleteNode(T dat) {
nCount--;
root.delete(dat, comp);
}
/**
* Get the root of the tree.
*
* @return The root of the tree.
*/
public ITreePart<T> getRoot() {
return root;
}
/**
* Check if a node is in the tree
*
* @param dat
* The node to check the presence of for the tree.
* @return Whether or not the node is in the tree.
*/
public boolean isInTree(T dat) {
return root.contains(dat, comp);
}
/**
* Traverse the tree in a specified way until the function fails
*
* @param tlm
* The way to linearize the tree for traversal
* @param p
* The function to use until it fails
*/
public void traverse(TreeLinearizationMethod tlm, Predicate<T> p) {
root.forEach(tlm, p);
}
/**
* Remove all soft-deleted nodes from the tree.
*/
public void trim() {
List<T> nds = new ArrayList<>(nCount);
traverse(TreeLinearizationMethod.PREORDER, d -> {
nds.add(d);
return true;
});
root = null;
nds.forEach(d -> addNode(d));
}
}
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