题目 设计一个程序,计算组合数:C(m,r)=m!/(r!*(m-r)!),其中m,r为正整数,且m>r.分别求出C(4,2),C(6,4),C(8,7)的组合数.求阶乘和组合数分别用函数来实现.

实现如下：

def factorial(n):
    """
    计算阶乘
    """
    if n == 0:
        return 1
    else:
        return n * factorial(n-1)

def combination(m, r):
    """
    计算组合数
    """
    return factorial(m) // (factorial(r) * factorial(m-r))

# 求 C(4,2)
c1 = combination(4, 2)
print("C(4,2) = ", c1)

# 求 C(6,4)
c2 = combination(6, 4)
print("C(6,4) = ", c2)

# 求 C(8,7)
c3 = combination(8, 7)
print("C(8,7) = ", c3)

输出结果：

C(4,2) =  6
C(6,4) =  15
C(8,7) =  8