递归：n个项的和 [英] Recursion: Sum of series of n terms

问题描述

需要递归函数

系列是：1 + 2 * 3 + 3 * 4 * 5 + 4 * 5 * 6 * 7 + ....

Series is: 1 + 2*3 + 3*4*5 + 4*5*6*7 + ....

递归查找n的序列之和。我无法考虑应该在函数中传递哪些参数。

Find the sum of the series for n recursively. I am not able to think of what parameters should I pass in function.

我的方法

我以为我应该传递n，要相乘的项数，但我无法想到的是，在同一函数中我应该如何+和*，我的return语句将是什么？

I thought that I should pass n, number of terms to be multiplied but what I am not able to think of is how should I + and * in same function and what will my return statement is?

推荐答案

function F(n, nmax, prod): Int
   //prod = (prod div n) * (2 * n) * (2 * n + 1)  simpler:  
   prod = prod * 2 * (2 * n + 1)  
   if n = nmax - 1
      return prod
   else
      return prod + F(n+1, nmax,  prod)

output F(1, 7, 1)

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