balls Time Limit: 20 Sec Memory Limit: 256 MB 题目连接 http://acm.hdu.edu.cn/showproblem.php?pid=5570 Description There are n balls with m colors. The possibility of that the color of the i-th ball is color j is ai,jai,1+ai,2+...+ai,m. If the number of b…

Problem Description There are n balls with m colors. The possibility of that the color of the i-th ball +ai,+...+ai,m. If the number of balls with the j-th is x, then you should pay x2 as the cost. Please calculate the expectation of the cost. Input…

 Balls and Boxes(盒子与球) Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others) Description 题目描述 Mr. Chopsticks is interested in random phenomena, and he conducts an experiment to study randomness. In the experiment, he thr…

对长为L的棒子随机取一点分割两部分,抛弃左边一部分,重复过程,直到长度小于d,问操作次数的期望. 区域赛的题,比较基础的概率论,我记得教材上有道很像的题,对1/len积分,$ln(L)-ln(d)+1$. /** @Date : 2017-10-06 14:32:03 * @FileName: HDU 5984 数学期望.cpp * @Platform: Windows * @Author : Lweleth (SoungEarlf@gmail.com) * @Link : https://gi…

balls  Accepts: 19  Submissions: 55  Time Limit: 6000/3000 MS (Java/Others)  Memory Limit: 65536/65536 K (Java/Others) 问题描述 有nn个球,共有mm种颜色,第ii个球的颜色为jj的概率为\frac{a_{i,j}}{a_{i,1}+a_{i,2}+...+a_{i,m}}​a​i,1​​+a​i,2​​+...+a​i,m​​​​a​i,j​​​​. 对于第ii种颜色,若有xx…

题意:你要从A到B去上班,然而这中间有n条河,距离为d.给定这n条河离A的距离p,长度L,和船的移动速度v,求从A到B的时间的数学期望. 并且假设出门前每条船的位置是随机的,如果不是在端点,方向也是不定的,你在陆地行走速度为1,输入保证河在AB之前,并且不会重叠. 析:一看这个题,好像不会啊...这怎么求,这么乱,这么复杂... 但是仔细一想求时间期望,不就是在过河的地方时间不是固定的么,只要求出过河的时间的数学期望,利用数学期望的线性,加起来就OK了. 这样一想感觉就不乱了,那么怎么求每个河的…

Problem Description Sakura has a very magical tool to paint walls. One day, kAc asked Sakura to paint a wall that looks like an M×N matrix. The wall has M×N squares in all. In the whole problem we denotes (x,y) to be the square at the x-th row, y-th…

题目地址:http://acm.hdu.edu.cn/showproblem.php?pid=4611 题意:给你一个N.A.B,要你求 AC代码: #include <iostream> #include <cstdio> #include <cstring> #include <string> #include <cstdlib> #include <cmath> #include <vector> #include…

Balls Rearrangement Time Limit: 9000/3000 MS (Java/Others)    Memory Limit: 65535/32768 K (Java/Others)Total Submission(s): 25    Accepted Submission(s): 8 Problem Description Bob has N balls and A boxes. He numbers the balls from 0 to N-1, and numbe…

这道题的概率可以单独考虑每个格子对期望的贡献值.因为其实每个格子是否被选都可以认为是独立的,单独一个格子贡献的期望为1*(该格子K次被选的概率),所以答案其实就是每个格子K次被选中的概率之和. #include <iostream> #include <cstdio> #include <cstring> #include <algorithm> #define LL long long using namespace std; int main(){ LL…