[Java][АПС] - InorderPredcessor (на еден јазел)

//package binarysearchtree;

// BinarySearchTree class

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Random;

//
// CONSTRUCTION: with no initializer
//
// ******************PUBLIC OPERATIONS*********************
// void insert( x )       --> Insert x
// void remove( x )       --> Remove x
// Comparable find( x )   --> Return item that matches x
// Comparable findMin( )  --> Return smallest item
// Comparable findMax( )  --> Return largest item
// boolean isEmpty( )     --> Return true if empty; else false
// void makeEmpty( )      --> Remove all items
// void printTree( )      --> Print tree in sorted order
/**
 * Implements an unbalanced binary search tree.
 * Note that all "matching" is based on the compareTo method.
 * @author Mark Allen Weiss
 */
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
        }
    }
    public E predeCessor(BNode<E> node) {
    	return predeCessor(root,node);
    }
    public E predeCessor(BNode<E> root,BNode<E> node) {
    	if(node.left!=null) {
    		return findMax(node.left).info;
    	}
    	else {
    		BNode<E> store = new BNode<E>();
    		while(root!=node) {
    			if(root.info.compareTo(node.info)<0) {
    				store = root;
    				root = root.right;
    			}
    			else {
    				root = root.left;
    			}
    		}
    		return store.info;
    	}
    }

    /**
     * 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);
        }
    }

    // Test program
    public static void main(String[] args) {
        int i,j,k;

        Random r = new Random(System.currentTimeMillis());
        BinarySearchTree<Integer> bst = new BinarySearchTree<Integer>();

        for (i=0;i<1000;i++)
            bst.insert(r.nextInt(1000000));

        bst.printTree();

    }
}

class BNode<E> {

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

    static int LEFT = 1;
    static int RIGHT = 2;

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

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

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

}

public class InOrderPredecessor {

	public static void main(String[] args) throws Exception, IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int n = Integer.parseInt(br.readLine());

		BinarySearchTree<Integer> tree = new BinarySearchTree<Integer>();
		for(int i=0;i<n;i++)
			tree.insert(Integer.parseInt(br.readLine()));

		int sebara = Integer.parseInt(br.readLine());
		BNode<Integer> node = tree.find(sebara);
		System.out.println(tree.predeCessor(node));
	}

}