快速查找排前面100的数!速度特快

package com.huawei.lzw.test;



import java.util.ArrayList;

import java.util.List;

import java.util.Random;



public class Test {

    public static void main(String[] args) {

	int[] arr = Test.getData(10);

	

	long begin = System.currentTimeMillis();

	Test.findTop(arr, 2);

	long end = System.currentTimeMillis();

	System.out.println("耗时:" + (end - begin) + "毫秒");

    }



    public static void findTop(int[] arr, int topCount) {

	int maxVal = Integer.MIN_VALUE;

	for (int i = 0; i < arr.length; i++) {

	    if (arr[i] > maxVal) {

		maxVal = arr[i];

	    }

	}

	int[] tempArr = new int[maxVal + 1];



	for (int i = 0; i < arr.length; i++) {

	    // System.out.println(arr[i] + "--" + tempArr[arr[i]]);

	    tempArr[arr[i]] = tempArr[arr[i]] + 1;

	}



	List<Integer> result = new ArrayList<Integer>();

	for (int i = maxVal; i >= 0; i--) {

	    if (tempArr[i] >= 1) {

		if (tempArr[i] == 1 && result.size() < topCount) {

		    result.add(i);

		} else {

		    for (int j = 0; j < tempArr[i] & result.size() < topCount; j++) {

			result.add(i);

		    }

		}

	    }

	}

	System.out.println(result);

    }



    public static int[] getData(int n) {

	int[] datas = new int[n];

	for (int i = 0; i < n; i++) {

	    datas[i] = new Random().nextInt(n);

	}

	return datas;

    }

}