知乎上看到一个问题,如果一个女人说自己集齐了12个星座的男朋友,那么她已经搞过多少男人了. 先考虑这个问题的最简单版本,如果说该女人每一次和12个星座的男人交往的概率相同. 考虑$dp$ 注意到这个问题正向十分不好推(因为如果用f表示从开始到当前的状态的话,只能由当前f推到 对应拓扑图上后面的f). 考虑从后面推到前面. $f_n$ 表示已经搞了 $n$ 种男人,搞到12种男人的期望步数. 这样 $f_n = \frac{n}{12} f_n  + \frac{12-n}{12} f_{n+1}…

如果一个女人遇到不同星座男的概率相同 那么这个女人期望遇到多少个男人就能集齐12个不同星座的男人 我们简化一下问题. 如果只有一个星座,那么期望值为1 如果只有两个星座,那遇到第一个男人后 期望再遇到两个人就能遇到另一个星座的男人 所以期望值为3 ...... 如果只有n个星座,那遇到过m种不同星座男后 期望再遇到n/(n - m)个人就能遇到另一个没遇到过的星座的男人 所以答案很明显了 double ans = 0 for(int i = 1;i <= 12;i++) ans += 12.0…

作者网址: https://my.oschina.net/shipley/blog/98973 背景:      前几天有人发了一个关于下面问题的贴,对这个有点好奇,故花时间做了点研究.        对单个反斜杠字符串替换成双斜杠的Java实现如下:    String s = "\\";    方法一:String sr1 = s.replaceAll("\\\\", "\\\\\\\\");    方法二:String sr1 = s.re…

这是六个人的故事,从不服输而又有强烈控制欲的monica,未经世事的千金大小姐rachel,正直又专情的ross,幽默风趣的chandle,古怪迷人的phoebe,花心天真的joey——六个好友之间的情路坎坷,事业成败和生活中的喜怒哀乐,无时无刻不牵动着彼此的心,而正是正平凡的点点滴滴,却成为最令人感动与留恋的东西. 人物:1.瑞秋•格林(RACHEL GREENE)由珍妮佛•安妮斯顿(Jennifer Aniston)扮演 瑞秋是莫妮卡的高中同学,在与牙医未婚夫的婚礼上脱逃至莫妮卡处. 2.罗…

Season 1, Episode 20: Tonight -Pope: I want him under 24hour surveillance. surveillance: 监视 保证24小时监视住他 -Sarah: I have to be there when they kill this man. kill: 杀掉 他们行刑的时候我必须在那里 The least you could do is review his case. least: 最少 review: 检阅 case: 情形…

2012.12.26 Hi all, How are you doing? Merry post-Christmas and happy upcoming New year!! I wish you had a good one this year. Our one week one time English corner is coming back! Are you excited to hear that. I know that you cannot wait to join us. Y…

Description Presumably, you all have known the question of stable marriage match. A girl will choose a boy; it is similar as the game of playing house we used to play when we are kids. What a happy time as so many friends playing together. And it is…

转载请注明出处: http://www.cnblogs.com/fraud/          ——by fraud Marriage Match II Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)Total Submission(s): 2410    Accepted Submission(s): 820 Problem Description Presumably, y…

Marriage Match II Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others) Total Submission(s): 1608    Accepted Submission(s): 566 Problem Description Presumably, you all have known the question of stable marriage match. A…

HDU 3081 Marriage Match II (网络流,最大流,二分,并查集) Description Presumably, you all have known the question of stable marriage match. A girl will choose a boy; it is similar as the game of playing house we used to play when we are kids. What a happy time as…