请问:既然quick selection 理论上证明是linear,比heap selection快。那为什么 top k 的问题都用heap 呢? 按理说应该用最快的quick selection啊。
w*n
2 楼
8,9个的时候能做不?
a*6
3 楼
【 以下文字转载自 Military 讨论区 】 发信人: abcxyz2046 (灌君), 信区: Military 标 题: 扭腰时报醒世好文:美国股市不再是经济的晴雨表 发信站: BBS 未名空间站 (Tue Feb 15 10:50:19 2011, 美东) 换句话说,中国股市输出价值观,华尔街不再是美国经济的晴雨表,而成了投机巨头们 独享的乐园。 http://www.nytimes.com/2011/02/14/opinion/14Salmon.html?src=me& Wall Street’s Dead End (华尔街的穷途末路) By FELIX SALMON (作者:菲利克斯.沙门鱼) 。。。 But look at America’s stock exchanges more closely, and there’s less to them than meets the eye. In truth, the stock market is becoming increasingly irrelevant — a trend that threatens the core principles of American capitalism. 。。。可是,如果近观美国股市,远非像表面看起来那么吸引人的眼球。实际上,股市 和经济渐行渐远,这种势头在威胁美帝的核心价值。 These days a healthy stock market doesn’t mean a healthy economy, as a glance at the high unemployment rate or the low labor-market participation rate will show. The Tea Party is right about one thing: What’s good for Wall Street isn’t necessarily good for Main Street. And the Germans aren’t buying the New York Stock Exchange for its commoditized, highly competitive and ultra-low-margin stock business, but rather for its lucrative derivatives operations. 这年头,良好的股市不再是经济的晴雨表,这个从居高不下的下岗率就能看出。奶茶党 有一个说法是对的:华尔街的利好不一定是 P民街之福。德国人参与华尔街的大交易仅 仅是为了金融衍生这颗摇钱树。 The stock market is still huge, of course: the companies listed on American exchanges are valued at more than $17 trillion, and they’re not going to disappear in the foreseeable future. But the glory days of publicly traded companies dominating the American business landscape may be over. The number of companies listed on the major domestic exchanges peaked in 1997 at more than 7,000, and it has been falling ever since. It’s now down to about 4,000 companies, and given its steep downward trend will surely continue to shrink. Nor are the remaining stocks an obvious proxy for the health of the American economy. Innovative American companies like Apple and Google may be worth hundreds of billions of dollars, but most of them don’t pay dividends or employ many Americans, and their shares are essentially speculative investments for people making a bet on how we’re going to live in the future. ......
n*x
4 楼
我的理解是quick selection只能handle有限集合,heap可以搞stream
【在 b*********e 的大作中提到】 : 请问:既然quick selection 理论上证明是linear,比heap selection快。那为什么 : top k 的问题都用heap 呢? : 按理说应该用最快的quick selection啊。
p*5
5 楼
over 14 days
h*n
6 楼
巧了,我今天就被问了这个,我先用了heap然后让我写quick select没写出来 真丢人
【在 b*********e 的大作中提到】 : 请问:既然quick selection 理论上证明是linear,比heap selection快。那为什么 : top k 的问题都用heap 呢? : 按理说应该用最快的quick selection啊。