Rename package root

The package root is now bjc, not io.github.bculkin2442.

1 files changed, 224 insertions, 0 deletions

diff --git a/src/main/java/bjc/funcdata/bst/BinarySearchTree.java b/src/main/java/bjc/funcdata/bst/BinarySearchTree.java
new file mode 100644
index 0000000..d0319e4
--- /dev/null
+++ b/src/main/java/bjc/funcdata/bst/BinarySearchTree.java
@@ -0,0 +1,224 @@
+package bjc.funcdata.bst;
+
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.List;
+import java.util.function.Predicate;
+
+import bjc.funcdata.FunctionalList;
+import bjc.funcdata.IList;
+
+/**
+ * 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 final Comparator<T> comparator;
+
+	/* The current count of elements in the tree */
+	private int elementCount;
+
+	/* The root element of the tree */
+	private ITreePart<T> root;
+
+	/**
+	 * Create a new tree using the specified way to compare elements.
+	 *
+	 * @param cmp
+	 *        The thing to use for comparing elements
+	 */
+	public BinarySearchTree(final Comparator<T> cmp) {
+		if(cmp == null) throw new NullPointerException("Comparator must not be null");
+
+		elementCount = 0;
+		comparator = cmp;
+	}
+
+	/**
+	 * Add a node to the binary search tree.
+	 *
+	 * @param element
+	 *        The data to add to the binary search tree.
+	 */
+	public void addNode(final T element) {
+		elementCount++;
+
+		if(root == null) {
+			root = new BinarySearchTreeNode<>(element, null, null);
+		} else {
+			root.add(element, comparator);
+		}
+	}
+
+	/**
+	 * Check if an adjusted pivot falls with the bounds of a list.
+	 *
+	 * @param elements
+	 *        The list to get bounds from.
+	 *
+	 * @param pivot
+	 *        The pivot.
+	 *
+	 * @param pivotAdjustment
+	 *        The distance from the pivot.
+	 *
+	 * @return Whether the adjusted pivot is with the list.
+	 */
+	private boolean adjustedPivotInBounds(final IList<T> elements, final int pivot, final int pivotAdjustment) {
+		return ((pivot - pivotAdjustment) >= 0) && ((pivot + pivotAdjustment) < elements.getSize());
+	}
+
+	/**
+	 * Balance the tree, and remove soft-deleted nodes for free.
+	 *
+	 * Takes O(N) time, but also O(N) space.
+	 */
+	public void balance() {
+		final IList<T> elements = new FunctionalList<>();
+
+		/* Add each element to the list in sorted order. */
+		root.forEach(TreeLinearizationMethod.INORDER, element -> elements.add(element));
+
+		/* Clear the tree. */
+		root = null;
+
+		/* Set up the pivot and adjustment for readding elements. */
+		final int pivot = elements.getSize() / 2;
+		int pivotAdjustment = 0;
+
+		/* Add elements until there aren't any left. */
+		while(adjustedPivotInBounds(elements, pivot, pivotAdjustment)) {
+			if(root == null) {
+				/* Create a new root element. */
+				root = new BinarySearchTreeNode<>(elements.getByIndex(pivot), null, null);
+			} else {
+				/*
+				 * Add the left and right elements in a balanced
+				 * manner.
+				 */
+				root.add(elements.getByIndex(pivot + pivotAdjustment), comparator);
+				root.add(elements.getByIndex(pivot - pivotAdjustment), comparator);
+			}
+
+			/* Increase the distance from the pivot. */
+			pivotAdjustment++;
+		}
+
+		/* Add any trailing unbalanced elements. */
+		if(pivot - pivotAdjustment >= 0) {
+			root.add(elements.getByIndex(pivot - pivotAdjustment), comparator);
+		} else if(pivot + pivotAdjustment < elements.getSize()) {
+			root.add(elements.getByIndex(pivot + pivotAdjustment), comparator);
+		}
+	}
+
+	/**
+	 * 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 element
+	 *        The node to delete
+	 */
+	public void deleteNode(final T element) {
+		elementCount--;
+
+		root.delete(element, comparator);
+	}
+
+	/**
+	 * 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 element
+	 *        The node to check the presence of for the tree..
+	 *
+	 * @return Whether or not the node is in the tree.
+	 */
+	public boolean isInTree(final T element) {
+		return root.contains(element, comparator);
+	}
+
+	/**
+	 * Traverse the tree in a specified way until the function fails.
+	 *
+	 * @param linearizationMethod
+	 *        The way to linearize the tree for traversal.
+	 *
+	 * @param traversalPredicate
+	 *        The function to use until it fails.
+	 */
+	public void traverse(final TreeLinearizationMethod linearizationMethod, final Predicate<T> traversalPredicate) {
+		if(linearizationMethod == null) {
+			throw new NullPointerException("Linearization method must not be null");
+		} else if(traversalPredicate == null) {
+			throw new NullPointerException("Predicate must not be nulls");
+		}
+
+		root.forEach(linearizationMethod, traversalPredicate);
+	}
+
+	/** Remove all soft-deleted nodes from the tree. */
+	public void trim() {
+		final List<T> nodes = new ArrayList<>(elementCount);
+
+		/*
+		 * Add all non-soft deleted nodes to the tree in insertion
+		 * order.
+		 */
+		traverse(TreeLinearizationMethod.PREORDER, node -> {
+			nodes.add(node);
+			return true;
+		});
+
+		/* Clear the tree. */
+		root = null;
+
+		/* Add the nodes to the tree in the order they were inserted. */
+		nodes.forEach(node -> addNode(node));
+	}
+
+	@Override
+	public String toString() {
+		return String.format("BinarySearchTree [elementCount=%s, root='%s']", elementCount, root);
+	}
+
+	@Override
+	public int hashCode() {
+		final int prime = 31;
+		int result = 1;
+		result = prime * result + elementCount;
+		result = prime * result + (root == null ? 0 : root.hashCode());
+		return result;
+	}
+
+	@Override
+	public boolean equals(final Object obj) {
+		if(this == obj) return true;
+		if(obj == null) return false;
+		if(!(obj instanceof BinarySearchTree<?>)) return false;
+
+		final BinarySearchTree<?> other = (BinarySearchTree<?>) obj;
+
+		if(elementCount != other.elementCount) return false;
+		if(root == null) {
+			if(other.root != null) return false;
+		} else if(!root.equals(other.root)) return false;
+
+		return true;
+	}
+}