原文:

给定三个整数 n 、 m 、 x 。任务是找到在 x 个袋子中分配 m 个物品的概率，使得第一个袋子包含 n 个物品 示例:

输入: m = 7，x =3，n = 3 输出:0.2 3 袋装 7 件的方式数为。 2 袋装 4 件物品的方式数量为。因为第一个包里有 3 样东西。 概率为// 输入: m = 9，x = 3，n = 4 /输出: 0.142857

进场: 一般来说，k 袋放置 n 件物品的方式数量为。

  • 将 m 个物品保存在 x 个袋子中的方法数量为。
  • 将(m-n)个物品保存在(x-1)个袋子中的方法数量为。因为第一个包包含 n 个项目。
  • 概率为 / 。

以下是上述方法的实现:

c 

// cpp program to find probability of
// first bag to contain n items such
// that m items are distributed among x bags
#include 
using namespace std;
// function to find factorial of a number
int factorial(int n)
{
    if (n <= 1)
        return 1;
    return n * factorial(n - 1);
}
// function to find ncr
int ncr(int n, int r)
{
    return factorial(n) / (factorial(r) * factorial(n - r));
}
// function to find probability of
// first bag to contain n items such
// that m items are distributed among x bags
float probability(int m, int n, int x)
{
    return (float)(ncr(m - n - 1, x - 2) /
                    (ncr(m - 1, x - 1) * 1.0));
}
// driver code
int main()
{
    int m = 9, x = 3, n = 4;
    // function call
    cout << probability(m, n, x);
    return 0;
}

java 语言(一种计算机语言，尤用于创建网站)

// java program to find probability of
// first bag to contain n items such
// that m items are distributed among x bags
class gfg
{
    // function to find factorial of a number
    public static int factorial(int n)
    {
        if (n <= 1)
            return 1;
        return n * factorial(n - 1);
    }
    // function to find ncr
    public static int ncr(int n, int r)
    {
        return factorial(n) / (factorial(r) * factorial(n - r));
    }
    // function to find probability of
    // first bag to contain n items such
    // that m items are distributed among x bags
    public static float probability(int m, int n, int x)
    {
        return (float) (ncr(m - n - 1, x - 2) / (ncr(m - 1, x - 1) * 1.0));
    }
    // driver code
    public static void main(string[] args)
    {
        int m = 9, x = 3, n = 4;
        // function call
        system.out.println(probability(m, n, x));
    }
}
// this code is contributed by
// sanjeev2552

python 3

# python3 program to find probability of
# first bag to contain n items such
# that m items are distributed among x bags
# function to find factorial of a number
def factorial(n) :
    if (n <= 1) :
        return 1;
    return n * factorial(n - 1);
# function to find ncr
def ncr(n, r) :
    return (factorial(n) / (factorial(r) *
                            factorial(n - r)));
# function to find probability of
# first bag to contain n items such
# that m items are distributed among x bags
def probability(m, n, x) :
    return float(ncr(m - n - 1, x - 2) /
                (ncr(m - 1, x - 1) * 1.0));
# driver code
if __name__ == "__main__" :
    m = 9; x = 3; n = 4;
    # function call
    print(probability(m, n, x));
# this code is contributed by ankitrai01

c

// c# program to find probability of
// first bag to contain n items such
// that m items are distributed among x bags
using system;
class gfg
{
    // function to find factorial of a number
    static int factorial(int n)
    {
        if (n <= 1)
            return 1;
        return n * factorial(n - 1);
    }
    // function to find ncr
    static int ncr(int n, int r)
    {
        return factorial(n) / (factorial(r) * factorial(n - r));
    }
    // function to find probability of
    // first bag to contain n items such
    // that m items are distributed among x bags
    static float probability(int m, int n, int x)
    {
        return (float) (ncr(m - n - 1, x - 2) / (ncr(m - 1, x - 1) * 1.0));
    }
    // driver code
    static void main()
    {
        int m = 9, x = 3, n = 4;
        // function call
        console.writeline(probability(m, n, x));
    }
}
// this code is contributed by
// mohitkumar 29

java 描述语言

output: 

0.142857

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