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…

题目链接 这题似乎就是纯概率论.. E(V)=D(X_i)=npq (p=1/m,p+q=1) #include<bits/stdc++.h> using namespace std; typedef long long LL; LL n,m; LL gcd(LL a,LL b) { return b?gcd(b,a%b):a; } int main() { while(cin>>n>>m && n+m) { LL a=n*m-n,b=m*m; LL g…

Balls and Boxes 题目链接: http://acm.hdu.edu.cn/showproblem.php?pid=5810 Description Mr. Chopsticks is interested in random phenomena, and he conducts an experiment to study randomness. In the experiment, he throws n balls into m boxes in such a manner t…

Balls and Boxes 题目连接: http://acm.hdu.edu.cn/showproblem.php?pid=5810 Description Mr. Chopsticks is interested in random phenomena, and he conducts an experiment to study randomness. In the experiment, he throws n balls into m boxes in such a manner t…

poj 2096 题目:http://poj.org/problem?id=2096 f[ i ][ j ] 表示收集了 i 个 n 的那个. j 个 s 的那个的期望步数. #include<cstdio> #include<cstring> #include<algorithm> #define db double using namespace std; ; db n,s,f[N][N]; int main() { scanf("%lf%lf"…

Balls Rearrangement 题目连接: http://acm.hdu.edu.cn/showproblem.php?pid=4611 Description Bob has N balls and A boxes. He numbers the balls from 0 to N-1, and numbers the boxes from 0 to A-1. To find the balls easily, he puts the ball numbered x into the…