面试题：m个长度为n的ordered array，求top k 个 数字

package com.sinaWeibo.interview;

import java.util.Comparator;
import java.util.Iterator;
import java.util.TreeSet;

/**
 * @Author: weblee
 * @Email: likaiweb@163.com
 * @Blog: http://www.cnblogs.com/lkzf/
 * @Time: 2014年10月25日下午5:22:58
 * 
 *************        function description *************** m个长度为n的ordered array，求top
 *        k 个 数字 *
 ****************************************************
 */

public class Top1000From2000Arrays {
    /*
     * 从m个数组中各取一个数，并记录每个数的来源数组，建立一个含k个元素的大根堆。
     * 此时堆顶就是最大的数，取出堆顶元素，并从堆顶元素的来源数组中取下一个数加入堆，再取最大值，一直这样进行k次即可。
     * 时间复杂度：k*log2(20)
     */
    public static int[] maxK(final int k, int[][] arrays) {
    int count = 0;
    Node max = null;
    int[] result = new int[k];

    TreeSet<Node> set = new TreeSet<Node>(new NodeComparator());

    set.add(new Node(arrays[0][0], 0, 0));

    for (int i = 0; i < arrays.length; i++) {
        if (set.first().value < arrays[i][arrays[i].length - 1]) {
        set.add(new Node(arrays[i][arrays[i].length - 1], i,
            arrays[i].length - 1));

        if (set.size() > k) {
            
            
            max = set.first();
            result[count++] = max.value;
            set.remove(set.first());
            set.add(new Node(arrays[max.originX][max.originY - 1], max.originX,
                max.originY - 1));
            
         // testing
            Iterator<Node> iter = set.iterator();
            while (iter.hasNext()) {
            System.out.print(iter.next().value + "	");
            }
            System.out.println();
            // testing
        }
        }
    }

    while (true) {
        max = set.first();
        result[count++] = max.value;

        if (count == k) {
        break;
        }
        
        set.remove(set.first());
        set.add(new Node(arrays[max.originX][max.originY - 1], max.originX,
            max.originY - 1));

        // testing
        Iterator<Node> iter = set.iterator();
        while (iter.hasNext()) {
        System.out.print(iter.next().value + "	");
        }
        System.out.println();
        // testing
    }

    return result;
    }

    public static void main(String[] args) {
    int[][] arrays = { { 4, 5, 6, 12 }, { 1, 2, 3, 45 }, { 3, 4, 5, 89 },
        { 101, 102, 103, 189 },{ 11, 12, 13, 289 } };

    int[] result = maxK(4, arrays);

    for (int num : result) {
        System.out.print(num + "	");
    }
    }

}

class Node {
    int value;
    int originX;
    int originY;

    public Node(int value, int originX, int originY) {
    this.value = value;
    this.originX = originX;
    this.originY = originY;
    }
}

class NodeComparator implements Comparator<Node> {

    @Override
    public int compare(Node o1, Node o2) {
    // TODO Auto-generated method stub
    return -(o1.value - o2.value);
    }

}