zoukankan      html  css  js  c++  java
  • Codeforces Round #253 (Div. 1) B. Andrey and Problem

    B. Andrey and Problem
    time limit per test
    2 seconds
    memory limit per test
    256 megabytes
    input
    standard input
    output
    standard output

    Andrey needs one more problem to conduct a programming contest. He has n friends who are always willing to help. He can ask some of them to come up with a contest problem. Andrey knows one value for each of his fiends — the probability that this friend will come up with a problem if Andrey asks him.

    Help Andrey choose people to ask. As he needs only one problem, Andrey is going to be really upset if no one comes up with a problem or if he gets more than one problem from his friends. You need to choose such a set of people that maximizes the chances of Andrey not getting upset.

    Input

    The first line contains a single integer n (1 ≤ n ≤ 100) — the number of Andrey's friends. The second line contains n real numbers pi(0.0 ≤ pi ≤ 1.0) — the probability that the i-th friend can come up with a problem. The probabilities are given with at most 6 digits after decimal point.

    Output

    Print a single real number — the probability that Andrey won't get upset at the optimal choice of friends. The answer will be considered valid if it differs from the correct one by at most 10 - 9.

    Sample test(s)
    input
    4
    0.1 0.2 0.3 0.8
    
    output
    0.800000000000
    
    input
    2
    0.1 0.2
    
    output
    0.260000000000
    
    Note

    In the first sample the best strategy for Andrey is to ask only one of his friends, the most reliable one.

    In the second sample the best strategy for Andrey is to ask all of his friends to come up with a problem. Then the probability that he will get exactly one problem is 0.1·0.8 + 0.9·0.2 = 0.26.


  • 相关阅读:
    高并发的优化策略
    Linux Ctrl+c与ctrl+z的区别
    数据库连接池的工作原理
    JDBC数据库连接池原理
    JSP页面批量选择&全选操作&选择回显
    通过火狐谋智查询API
    通过console.log()打印window对象的属性、方法、事件
    制作 首页
    JavaScript 函数参数
    JavaScript 函数
  • 原文地址:https://www.cnblogs.com/bhlsheji/p/4384771.html
Copyright © 2011-2022 走看看