题目连接：uva 10491 - Cows and Cars 题目大意：给出a，b和c，表示有a + b 个门， a个后面是牛， b个后面是车， 然后你从中选一个门，之后有一个知情人帮你打开c个后面是牛的门（因为1≤c< a，所以就算第一次选中牛，知情人还是可以打开c个门），然后你在没有打开的门中选一个，问说第二次选得门后面是车的概率。 解题思路：问题可以分成两种情况: 1)第一

原题： In television contests, participants are often asked to choose one from a set of or doors for example, one or several of which lead to different prizes. In this problem we will deal with a speci

#include <bits/stdc++.h>using namespace std;int main(int argc, char const *argv[]){double a, b, c;while (cin >> a >> b >> c)printf("%.5f\n", b * (a + b - 1) / (a + b) / (a + b - c - 1));return 0;}