求阶乘及阶乘和

 1 #求阶乘方法一
 2 def f1(n)
 3   if n == 1
 4     return 1 
 5   else
 6     return n * f1(n-1)
 7   end
 8 end
 9 
10 #求阶乘方法二
11 def f2(n)
12   i = 1
13   while n > 0
14     i *= n
15     n -= 1
16   end
17   return i
18 end
19  
20 #求1到n的阶乘之和方法一
21 sum = 0
22 (1..43).each do | x |
23   sum = sum + f2(x)      
24 end
25 puts sum
26 
27 #求1到n的阶乘之和方法二
28 def f3(n)
29   sum = 0
30   n.downto(1) do
31     while n > 0
32       i = 1
33       i *= n
34       n -= 1
35       sum *= i
36       sum += i
37     end
38   end    
39   return sum
40 end
41 puts f3(43)
42 
43