kungfu.algdesign.ds.MovingMedian.java Source code

Introduction

Here is the source code for kungfu.algdesign.ds.MovingMedian.java

Source

/*
 * Copyright (C) 2014 - present, Laszlo Csontos
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 * 
 */

package kungfu.algdesign.ds;

import java.util.Queue;

import com.google.common.collect.MinMaxPriorityQueue;

/**
 * @author lcsontos
 */
public class MovingMedian {

    public static void calculate(Queue<Integer> data, Queue<Integer> medians) {
        MinMaxPriorityQueue<Integer> minHeap = MinMaxPriorityQueue.create();
        MinMaxPriorityQueue<Integer> maxHeap = MinMaxPriorityQueue.create();

        minHeap.add(Integer.MIN_VALUE);
        maxHeap.add(Integer.MAX_VALUE);

        Integer item = null;
        Integer median = null;

        while ((item = data.poll()) != null) {
            if (median == null) {
                maxHeap.add(item);
            } else if (item >= median) {
                maxHeap.add(item);
            } else {
                minHeap.add(item);
            }

            if (maxHeap.size() - minHeap.size() == 2) {
                minHeap.add(maxHeap.pollFirst());
            } else if (minHeap.size() - maxHeap.size() == 2) {
                maxHeap.add(minHeap.pollLast());
            }

            if (minHeap.size() == maxHeap.size() || minHeap.size() > maxHeap.size()) {
                median = minHeap.peekLast();
            } else {
                median = maxHeap.peekFirst();
            }

            medians.add(median);
        }
    }

}