原文:
给定两枚分别具有获得人头 p% 和 q% 概率的硬币，任务是在给定硬币中随机选择硬币后，确定获得两个连续人头的概率。 例:
输入: p = 33，q = 66 输出:0.55000000000000 输入: p = 33，q = 66 输出:0.5500000000000
方法: 由于两个硬币不相同，因此将用于获得期望的概率。 由于硬币是随机选择的，因此可以选择其中任何一种，因此计算中将包括 p 和 q 。应用贝叶斯定理后，需要的答案将是 (p * p q * q) / (p q) ，因为如果选择第一枚硬币，那么两个头像背对背的概率是 p * p ，第二枚硬币也是一样。 是贝叶斯定理的应用。
p(b | a)= p(a |^| b)/p(a)=(1/2 * p * p 1/2 * q * q)/(1/2 * p 1/2 * q)=(p * p q * q)/(p q)其中: p(b) =第二次投掷获得人头的概率， p(a) =第一次投掷获得人头的概率， p(a |^| b) =两次投掷都获得人头的概率。 所以，p(b | a)是第二次投掷获得人头的概率，前提是我们在第一次投掷中获得人头 。 此处 a、b 表示第 1、2 枚硬币。
以下是上述方法的实现:
c
// c program to get the probability
// of getting two consecutive heads
#include
using namespace std;
// function to return the probability
// of getting two consecutive heads
double getprobability(double p, double q)
{
p /= 100;
q /= 100;
// formula derived from bayes's theorem
double probability = (p * p q * q) / (p q);
return probability;
}
// driver code
int main()
{
double p, q;
// given the probability of getting
// a head for both the coins
p = 80;
q = 40;
cout << fixed
<< setprecision(15)
<< getprobability(p, q)
<< endl;
return 0;
}
java 语言(一种计算机语言，尤用于创建网站)
// java program to get the probability
// of getting two consecutive heads
import java.io.*;
class gfg {
// function to return the probability
// of getting two consecutive heads
static double getprobability(double p, double q)
{
p /= 100;
q /= 100;
// formula derived from bayes's theorem
double probability = (p * p q * q) / (p q);
return probability;
}
// driver code
public static void main (string[] args) {
double p, q;
// given the probability of getting
// a head for both the coins
p = 80;
q = 40;
system.out.println( getprobability(p, q));
}
}
// this code is contributed by anuj_67..
python 3
# python 3 program to get the probability
# of getting two consecutive heads
# function to return the probability
# of getting two consecutive heads
def getprobability(p, q):
p /= 100
q /= 100
# formula derived from bayes's theorem
probability = (p * p q * q) / (p q)
return probability
# driver code
if __name__ == "__main__":
# given the probability of getting
# a head for both the coins
p = 80
q = 40
print(getprobability(p, q))
# this code is contributed
# by chitranayal
c
// c# program to get the probability
// of getting two consecutive heads
using system;
class gfg {
// function to return the probability
// of getting two consecutive heads
static double getprobability(double p, double q)
{
p /= 100;
q /= 100;
// formula derived from bayes's theorem
double probability = (p * p q * q) / (p q);
return probability;
}
// driver code
public static void main () {
double p, q;
// given the probability of getting
// a head for both the coins
p = 80;
q = 40;
console.writeline( getprobability(p, q));
}
}
// this code is contributed by inder_verma..
服务器端编程语言（professional hypertext preprocessor 的缩写）
java 描述语言
output:
0.666666666666667
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