求阶乘及阶乘和

 

 

#求阶乘方法一
def f1(n)
  if n == 1
    return 1 
  else
    return n * f1(n-1)
  end
end

#求阶乘方法二
def f2(n)
  i = 1
  while n > 0
    i *= n
    n -= 1
  end
  return i
end
 
#求1到n的阶乘之和方法一
sum = 0
(1..43).each do | x |
  sum = sum + f2(x)      
end
puts sum

#求1到n的阶乘之和方法二
def f3(n)
  sum = 0
  n.downto(1) do
    while n > 0
      i = 1
      i *= n
      n -= 1
      sum *= i
      sum += i
    end
  end    
  return sum
end
puts f3(43)