列表理解：列出列表 [英] List comprehension: making lists of lists

问题描述

嗨im试图在haskell中使用数字a的一个函数使用列表的一个部分，例如数字 4 它会创建 [[1,1,1,1]，[1,1,2]，[1,3]，[2,2]，[4]] 。我正在考虑使用列表理解来创建列表x，然后使用[1 ... n]中的数字（n是我想要的分区编号）创建更多列表，其中创建列表的总和相等到n。

hi im trying to make a function in haskell that takes a number a makes a partion of it using lists i.e. for number 4 it would create [[1,1,1,1],[1,1,2],[1,3],[2,2],[4]]. I was thinking of using list comprehension for this where it would create list x and then create further lists using numbers from [1...n] (n being the partition number I would want) where the sum of the list created would be equal to n.

到目前为止我创建的代码是 -

The code I have created so far is-

partions (n:xs) = [[x|x<-[1...n], sum[x]==n]]|xs<-[1..]]

但很明显它不起作用，有什么建议吗？

but obiviously it doesnt work, any suggestions?

谢谢。

推荐答案

我建议尝试递归：要获得n的分区，遍历数字i = 1到n，并递归地生成分区（ni），基本情况是1的唯一分区本身是1，0的分区是空列表。

I suggest trying recursion: To obtain the partitions of n, iterate over the numbers i = 1 to n, and recursively generate the partitions of (n-i), the base case being that the only partition of 1 is 1 itself, and the partition of 0 is the empty list.

这篇关于列表理解：列出列表的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！