[ADSx] - Inorder Successor

import java.io.BufferedReader;
import java.io.InputStreamReader;

class BNode<E extends Comparable<E>> {

    public E info;
    public BNode<E> left;
    public BNode<E> right;

    public BNode(E info) {
        this.info = info;
        left = null;
        right = null;
    }

    public BNode(E info, BNode<E> left, BNode<E> right) {
        this.info = info;
        this.left = left;
        this.right = right;
    }

}

class BinarySearchTree<E extends Comparable<E>> {

    /**
     * The tree root.
     */
    private BNode<E> root;

    /**
     * Construct the tree.
     */
    public BinarySearchTree() {
        root = null;
    }

    /**
     * Insert into the tree; duplicates are ignored.
     *
     * @param x the item to insert.
     */
    public void insert(E x) {
        root = insert(x, root);
    }

    /**
     * Remove from the tree. Nothing is done if x is not found.
     *
     * @param x the item to remove.
     */
    public void remove(E x) {
        root = remove(x, root);
    }

    /**
     * Find the smallest item in the tree.
     *
     * @return smallest item or null if empty.
     */
    public E findMin() {
        return elementAt(findMin(root));
    }

    /**
     * Find the largest item in the tree.
     *
     * @return the largest item of null if empty.
     */
    public E findMax() {
        return elementAt(findMax(root));
    }

    /**
     * Find an item in the tree.
     *
     * @param x the item to search for.
     * @return the matching item or null if not found.
     */
    public BNode<E> find(E x) {
        return find(x, root);
    }

    /**
     * Make the tree logically empty.
     */
    public void makeEmpty() {
        root = null;
    }

    /**
     * Test if the tree is logically empty.
     *
     * @return true if empty, false otherwise.
     */
    public boolean isEmpty() {
        return root == null;
    }

    /**
     * Print the tree contents in sorted order.
     */
    public void printTree() {
        if (isEmpty()) {
            System.out.println("Empty tree");
        } else {
            printTree(root);
        }
    }

    /**
     * Internal method to get element field.
     *
     * @param t the node.
     * @return the element field or null if t is null.
     */
    private E elementAt(BNode<E> t) {
        if (t == null)
            return null;
        return t.info;
    }

    /**
     * Internal method to insert into a subtree.
     *
     * @param x the item to insert.
     * @param t the node that roots the tree.
     * @return the new root.
     */
    private BNode<E> insert(E x, BNode<E> t) {
        if (t == null) {
            t = new BNode<E>(x, null, null);
        } else if (x.compareTo(t.info) < 0) {
            t.left = insert(x, t.left);
        } else if (x.compareTo(t.info) > 0) {
            t.right = insert(x, t.right);
        } else ;  // Duplicate; do nothing
        return t;
    }

    /**
     * Internal method to remove from a subtree.
     *
     * @param x the item to remove.
     * @param t the node that roots the tree.
     * @return the new root.
     */
    private BNode<E> remove(Comparable x, BNode<E> t) {
        if (t == null)
            return t;   // Item not found; do nothing

        if (x.compareTo(t.info) < 0) {
            t.left = remove(x, t.left);
        } else if (x.compareTo(t.info) > 0) {
            t.right = remove(x, t.right);
        } else if (t.left != null && t.right != null) { // Two children
            t.info = findMin(t.right).info;
            t.right = remove(t.info, t.right);
        } else {
            if (t.left != null)
                return t.left;
            else
                return t.right;
        }
        return t;
    }

    /**
     * Internal method to find the smallest item in a subtree.
     *
     * @param t the node that roots the tree.
     * @return node containing the smallest item.
     */
    private BNode<E> findMin(BNode<E> t) {
        if (t == null) {
            return null;
        } else if (t.left == null) {
            return t;
        }
        return findMin(t.left);
    }

    /**
     * Internal method to find the largest item in a subtree.
     *
     * @param t the node that roots the tree.
     * @return node containing the largest item.
     */
    private BNode<E> findMax(BNode<E> t) {
        if (t == null) {
            return null;
        } else if (t.right == null) {
            return t;
        }
        return findMax(t.right);
    }

    /**
     * Internal method to find an item in a subtree.
     *
     * @param x is item to search for.
     * @param t the node that roots the tree.
     * @return node containing the matched item.
     */
    private BNode<E> find(E x, BNode<E> t) {
        if (t == null)
            return null;

        if (x.compareTo(t.info) < 0) {
            return find(x, t.left);
        } else if (x.compareTo(t.info) > 0) {
            return find(x, t.right);
        } else {
            return t;    // Match
        }
    }

    /**
     * Internal method to print a subtree in sorted order.
     *
     * @param t the node that roots the tree.
     */
    private void printTree(BNode<E> t) {
        if (t != null) {
            printTree(t.left);
            System.out.println(t.info);
            printTree(t.right);
        }
    }

    public E getSuccessor(BNode<E> node, E x) {
        BNode<E> target = find(x);
        if (target == null) return null;
        BNode<E> successor = null;
        BNode<E> current = node;
        while (current != null && !current.info.equals(target.info)) {
            if (current.info.compareTo(target.info) > 0) {
                successor = current;
                current = current.left;
            } else {
                current = current.right;
            }
        }
        if (current == null) return null;
        if (current.right == null) return successor.info;
        current = current.right;
        while (current.left != null) {
            current = current.left;
        }
        return current.info;
    }

    public E getSuccessor(E x) {
        return getSuccessor(root, x);
    }

}

public class InorderSuccessor {

    public static void main(String[] args) throws Exception {
        int i, j, k;

        BinarySearchTree<Integer> tree = new BinarySearchTree<Integer>();

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int N = Integer.parseInt(br.readLine());

        for (i = 0; i < N; i++) {
            int num = Integer.parseInt(br.readLine());
            tree.insert(new Integer(num));
        }

        br.close();

        /*tree.printTree();
        System.out.println();*/

        int prev = tree.findMin();
        System.out.println(prev);

        for (i = 1; i < N; i++) {
            int tmp = tree.getSuccessor(prev);
            System.out.println(tmp);
            prev = tmp;
        }

    }

}
/**
 * You are given a binary search tree.
 * Write a recursive function, inorderSuccessor,
 * which for a given value in the tree, will find its successor.
 * <p>
 * Name of class: InorderSuccessor
 */