Step by Step solution about How to resolve the algorithm Word wheel step by step in the Haskell programming language

The provided code is a Haskell program that implements a function to find words that can be formed from a given grid of letters, known as the Word Wheel problem. It reads a dictionary of words from a file and applies the gridWords function to each line of the dictionary to identify words that meet specific criteria:

1. Word Length: The word must be at least 3 characters long.

2. Central Letter: The middle letter of the word must match the middle letter of the grid.

3. Letters in Wheel: All the letters in the word must be present in the grid after sorting the letters of the grid alphabetically.

The gridWords function takes two parameters:

• grid: A list of strings representing the rows of the grid.

• dictionary: A list of strings representing the dictionary of words.

It first calculates the concatenated, lowercase letters of the grid (cs) and sorts them to create the "wheel" (wheel). The middle letter of the grid (mid) is also determined.

The wheelFit function checks if a word can be formed from the grid by comparing the sorted letters of the word to the sorted letters of the grid. It returns True if all letters in the word are present in the grid, and False otherwise.

The main function reads the dictionary from a file named "unixdict.txt." For each line in the dictionary, it applies the gridWords function to the line and the given grid ["NDE", "OKG", "ELW"]. Words that meet the criteria are then printed using putStrLn.

Overall, this code provides a solution to the Word Wheel problem by identifying words that can be formed from a given grid of letters while satisfying certain constraints.

import Data.Char (toLower)
import Data.List (sort)
import System.IO (readFile)

------------------------ WORD WHEEL ----------------------

gridWords :: [String] -> [String] -> [String]
gridWords grid =
  filter
    ( ((&&) . (2 <) . length)
        <*> (((&&) . elem mid) <*> wheelFit wheel)
    )
  where
    cs = toLower <$> concat grid
    wheel = sort cs
    mid = cs !! 4

wheelFit :: String -> String -> Bool
wheelFit wheel = go wheel . sort
  where
    go _ [] = True
    go [] _ = False
    go (w : ws) ccs@(c : cs)
      | w == c = go ws cs
      | otherwise = go ws ccs

--------------------------- TEST -------------------------
main :: IO ()
main =
  readFile "unixdict.txt"
    >>= ( mapM_ putStrLn
            . gridWords ["NDE", "OKG", "ELW"]
            . lines
        )