答复: 一道腾讯面试题:从大量数字中取出 top 100

从1亿个数字中取出最大的100个
JVM需要调到-Xmx1024M，以免溢出

public class findValue {
	
	public static void main(String[] args){
			
		int max = 10000*10000;
		int length=100;
		int ints[] = new int[max];
		Random random = new Random();
		for (int i=0;i<max;i++) {
			ints[i]=Math.abs(random.nextInt(max));
		}
		List<Integer> list = new ArrayList();

		long start = System.currentTimeMillis();
		int size=0;
		int value=0;
		list.add(ints[0]);
		for(int i=1;i<max;i++){
			value=ints[i];
			size=list.size();
			if(value<list.get(size-1)){
				if(size<length){
					list.add(value);
				}
				continue;
			}else if(value>list.get(0)){
				list.add(0,value);
				if(size==length){
					list.remove(size);
				}
				continue;
			}
			
			for(int j=0;j<size;j++){
				if(value>list.get(j)){
                                              //如果不需要排除重复数字，则去掉该判断
					if(j>0&&value!=list.get(j-1)){
						list.add(j,value);
						if(size==length){
						  list.remove(size);
						}
					}
					break;
				}
			 }
		}
		
		System.out.println("time:"+(System.currentTimeMillis()-start));
		
		System.out.println(list);
		TreeSet<Integer> set = new TreeSet();
		set.addAll(list);
		
		System.out.println(set.size()+":"+list.size());
		if(set.size()!=list.size()){
			System.out.println("error");
		}
		int i=0;
		for(Iterator<Integer> it=set.iterator();it.hasNext();){
			value=it.next();
			System.out.println(value+":"+list.get(list.size()-1-i));
			if(value!=list.get(list.size()-1-i)){
				System.out.println("error");
				break;
			}
			i++;
		}
	}
}

E2160 3G
time:2453