http://acm.sgu.ru/problem.php?contest=0&problem=495 题意:N个箱子M个人,初始N个箱子都有一个礼物,M个人依次等概率取一个箱子,如果有礼物则拿出礼物放回盒子,如果没有礼物则不操作.问M个人拿出礼物个数的期望.(N,M<=100000) #include <cstdio> using namespace std; double mpow(double a, int n) { double r=1; while(n) { if(n&…

水概率....SGU里难得的水题.... 495. Kids and Prizes Time limit per test: 0.5 second(s)Memory limit: 262144 kilobytes input: standardoutput: standard ICPC (International Cardboard Producing Company) is in the business of producing cardboard boxes. Recently the…

题目链接 495. Kids and Prizes Time limit per test: 0.25 second(s)Memory limit: 262144 kilobytes input: standardoutput: standard ICPC (International Cardboard Producing Company) is in the business of producing cardboard boxes. Recently the company organiz…

题意: N个礼品箱, 每个礼品箱内的礼品只有第一个抽到的人能拿到. M个小孩每个人依次随机抽取一个,  求送出礼品数量的期望值. 1 ≤ N, M ≤ 100, 000 挺水的说..设f(x)表示前x个人都选择完成后礼品剩下数的期望值( f(0) = N ), 那么f(x) = f(x - 1) - f(x - 1) / N = f(x - 1) * (N - 1) / N (显然). 那么答案就是等于 N - N * [(N - 1) / N]^M. 后面部分可以用快速幂优化.时间复杂度O(l…

http://acm.sgu.ru/problem.php?contest=0&problem=495 学习:当一条路走不通,换一种对象考虑,还有考虑对立面. 495. Kids and Prizes Time limit per test: 0.25 second(s)Memory limit: 262144 kilobytes input: standardoutput: standard ICPC (International Cardboard Producing Company) is…

题目链接:http://acm.sgu.ru/problem.php?contest=0&problem=495 题意: 有n个礼物盒,m个人. 最开始每个礼物盒中都有一个礼物. m个人依次随机选一个盒子,如果有礼物就拿走,然后放回空盒子. 问你所有人得到总礼物数的期望. 题解: 三种做法:期望dp,概率dp,推公式 一.期望dp 表示状态: dp[i] = 该第i个人拿箱子时的总礼物的期望 找出答案: ans = dp[m] 如何转移: 对于第i个人,拿到礼物或没拿到. (1)φ(没拿到) =…

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 日期 题目地址:https://leetcode.com/problems/teemo-attacking/description/ 题目描述 In LOL world, there is a hero called Teemo and his attacking can make his enemy Ashe be in poisoned cond…

495. Kids and Prizes Time limit per test: 0.25 second(s)Memory limit: 262144 kilobytes input: standardoutput: standard ICPC (International Cardboard Producing Company) is in the business of producing cardboard boxes. Recently the company organized a…

Tickets   Description Conductor is quite a boring profession, as all you have to do is just to sell tickets to the passengers. So no wonder that once upon a time in a faraway galaxy one conductor decided to diversify this occupation. Now this conduct…

time limit per test2 seconds memory limit per test256 megabytes inputstandard input outputstandard output Generous sponsors of the olympiad in which Chloe and Vladik took part allowed all the participants to choose a prize for them on their own. Chri…