Question

尝试在haskell中实现qwerty距离函数。作为其中的一部分，我想出了一个函数，它将在定义的结构（向量，列表，数组？）中返回特定元素的i，j索引。我被卡住了。

import qualified Data.Vector as V
qwerty = V.fromList $ map V.fromList
        [ "qwertyuiop", "asdfghjkl;'", "zxcvbnm,./" ]

Answer 1

您可以尝试以下内容：

import qualified Data.Vector as V

qwerty = V.fromList $ map V.fromList
        [ "qwertyuiop", "asdfghjkl;'", "zxcvbnm,./" ]

findElement :: Char -> Maybe (Int,Int)
findElement c = f $ V.findIndex (V.elem c) qwerty where
  f (Just i) = (,) i `fmap` (V.elemIndex c $ qwerty V.! i)
  f Nothing = Nothing

Answer 2

这是将索引与列表元素相关联的任务。通常这对zip [0..] xs很容易。因此，首先将索引与每个字符串相关联，然后将索引与字符串中的每个字符相关联。

import qualified Data.Map as M
qwmap = M.fromList $ concatMap f $ zip [0..] qwerty where
   qwerty = ["qwertyuiop[]", "asddfghjkl;'#", "zxcvbnm,./"]
   f (i,cs) = map (\(j,c) -> (c, (i,j))) $ zip [0..] cs

或者，如果您不关心重复elemIndex查找的线性成本：

import Data.List
qp a = foldr f Nothing $ zip [0..] qwerty where
   qwerty = ["qwertyuiop[]", "asddfghjkl;'#", "zxcvbnm,./"]
   f (p,xs) n = maybe n (Just . (p,)) $ elemIndex a xs

Haskell找到qwerty距离的2d指数

2 个答案: