BST.java

import java.util.LinkedList;
import java.util.Queue;

/**
 * Created by kiyan on 5/26/16.
 */
public class BST<Key extends Comparable<Key>, Value> {

    private Node root;

    public Value get(Key key) {
        Node x = root;
        while (x != null) {
            int cmp = key.compareTo(x.key);
            if (cmp < 0) {
                x = x.left;
            } else if (cmp > 0) {
                x = x.right;
            } else {
                return x.val;
            }
        }
        return null;
    }

    public void put(Key key, Value val) {
        root = put(root, key, val);
    }

    private Node put(Node x, Key key, Value val) {
        if (x == null) {
            return new Node(key, val);
        }
        int cmp = key.compareTo(x.key);
        if (cmp < 0) {
            x.left = put(x.left, key, val);
        } else if (cmp > 0) {
            x.right = put(x.right, key, val);
        } else {
            x.val = val;
        }
        x.count = 1 + size(x.left) + size(x.right);
        return x;
    }

    public Key floor(Key key) {
        Node x = floor(root, key);
        if (x == null) {
            return null;
        }
        return x.key;
    }

    private Node floor(Node x, Key key) {
        if (x == null) {
            return null;
        }

        int cmp = key.compareTo(x.key);
        if (cmp == 0) {
            return x; // found
        }

        if (cmp < 0) {
            return floor(x.left, key); // in left subtree
        }

        Node t = floor(x.right, key); // in right subtree
        if (t != null) {
            return t; // found in right
        }
        return x;
    }

    public int size() {
        return size(root);
    }

    private int size(Node x) {
        if (x == null) {
            return 0;
        }
        return x.count;
    }

    public int rank(Key key) {
        return rank(root, key);
    }

    private int rank(Node x, Key key) {
        if (x == null) {
            return 0;
        }
        int cmp = key.compareTo(x.key);
        if (cmp < 0) {
            return rank(x.left, key);
        } else if (cmp > 0) {
            return 1 + size(x.left) + rank(x.right, key); // current node + nodes in left subtree + right
        } else {
            return size(x.left);
        }
    }

    public Iterable<Key> keys() {
        Queue<Key> q = new LinkedList<>();
        inorder(root, q);
        return q;
    }

    private void inorder(Node x, Queue<Key> q) {
        if (x == null) {
            return;
        }
        inorder(x.left, q);
        q.offer(x.key);
        inorder(x.right, q);
    }

    public void deleteMin() {
        root = deleteMin(root);
    }

    private Node deleteMin(Node x) {
        if (x.left == null) {
            return x.right;
        }
        x.left = deleteMin(x.left);
        x.count = 1 + size(x.left) + size(x.right);
        return x;
    }

    public void delete(Key key) {
        root = delete(root, key);
    }

    /**
     * Hibbard deletion
     */
    private Node delete(Node x, Key key) {
        if (x == null) {
            return null;
        }
        int cmp = key.compareTo(x.key);
        if (cmp < 0) {
            x.left = delete(x.left, key);
        } else if (cmp > 0) {
            x.right = delete(x.right, key);
        } else {
            if (x.right == null) {
                return x.left;
            }
            if (x.left == null) {
                return x.right;
            }
            Node t = x;
            x = min(t.right);
            x.right = deleteMin(t.right);
            x.left = t.left;
        }
        x.count = 1 + size(x.left) + size(x.right);
        return x;
    }

    public Node min() {
        return min(root);
    }

    private Node min(Node x) {
        if (x == null || x.left == null) {
            return x;
        }
        return min(x.left);
    }

    class Node {

        private Key key;
        private Value val;
        private Node left;
        private Node right;
        private int count;

        public Node(Key key, Value val) {
            this.key = key;
            this.val = val;
        }
    }
}