4254：A Famous Game

题目描述

Mr. B and Mr. M like to play with balls. They have many balls colored in blue and red. Firstly, Mr. B randomly picks up N balls out of them and put them into a bag.
Mr. M knows that there are N+1 possible situations in which the number of red balls is ranged from 0 to N, and we assume the possibilities of the N+1 situations are
the same. But Mr. M does not know which situation occurs. Secondly, Mr. M picks up P balls out of the bag and examines them. There are Q red balls and P-Q blue
balls. The question is: if he picks up one more ball out of the bag, what is the possibility that this ball is red?

输入解释

Each test case contains only one line with three integers N, P and Q (2 <= N <= 100,000, 0 <= P <= N-1, 0 <= Q <= P).

输出解释

For each test case, display a single line containing the case number and the possibility of the next ball Mr. M picks out is red. The number should be rounded to four
decimal places.

输入样例

3 0 0
4 2 1

输出样例

Case 1: 0.5000
Case 2: 0.5000

提示

For example as the sample test one, there are three balls in the bag. The possibilities of the four possible situations are all 0.25. If there are no red balls in the bag, 
the possibility of the next ball are red is 0. If there is one red ball in the bag, the possibility is 1/3. If there are two red balls, the possibility is 2/3. Finally if all balls
are red, the possibility is 1. So the answer is 0*(1/4)+(1/3)*(1/4)+(2/3)*(1/4)+1*(1/4)=0.5.

来自杭电HDUOJ的附加信息

Recommend

该题目是Virtual Judge题目，来自杭电HDUOJ

题目来源 Fudan Local Programming Contest 2012

源链接： HDU-4254

最后修改于 2020-10-25T23:11:47+00:00 由爬虫自动更新

共提交 0 次

通过率 --%

时间上限	内存上限
2000/1000MS(Java/Others)	32768/32768K(Java/Others)