RedBlackNode

RedBlackNode is a Java implementation of red-black trees. By subclassing RedBlackNode, clients can add arbitrary data and augmentation information to each node. (self-balancing binary search tree, self-balancing BST, augment, augmented)

Features

• Supports min, max, root, predecessor, successor, insert, remove, rotate, split, concatenate, create balanced tree, LCA, and compare operations. The running time of each operation has optimal big O bounds.
• Supports arbitrary augmentation by overriding augment(). Examples of augmentation are the number of non-leaf nodes in a subtree and the sum of the values in a subtree.
• The parent and child links and the color are public fields. This gives clients flexibility. However, it is possible for a client to violate the red-black or BST properties.
• "Assert is valid" methods allow clients to check for errors in the structure or contents of a red-black tree. This is useful for debugging.
• As a bonus (a proof of concept and a test case), this includes the TreeList class, a List implementation backed by a red-black tree augmented by subtree size.
• Tested in Java 6.0 and 7.0. It might also work in Java 5.0.

Limitations

• The values of the tree must be stored in the non-leaf nodes. RedBlackNode does not support use cases where the values must be stored in the leaf nodes.
• Augmentations that depend on information stored in a node's ancestors are not (easily) supported. For example, augmenting each node with the number of nodes in the left subtree is not (easily and efficiently) supported, because in order to perform a right rotation, we would need to use the parent's augmentation information. However, RedBlackNode supports augmenting each node with the number of nodes in the subtree, which is basically equivalent.
• The running time of each operation has optimal big O bounds. However, beyond this, no special effort has been made to optimize performance.

Example

/** Red-black tree augmented by the sum of the values in the subtree. */
public class SumNode extends RedBlackNode<SumNode> {
    public int value;
    public int sum;

    public SumNode(int value) {
        this.value = value;
    }

    @Override
    public boolean augment() {
        int newSum = value + left.sum + right.sum;
        if (newSum == sum) {
            return false;
        } else {
            sum = newSum;
            return true;
        }
    }
}

Documentation

For more detailed instructions, check the source code to see the full API and Javadoc documentation.