From 485e005ea6e8d001bf15a1440a1609e775769e1f Mon Sep 17 00:00:00 2001
From: Danilo Reyes <CaptainJawZ@protonmail.com>
Date: Wed, 2 Apr 2025 22:03:13 -0600
Subject: [PATCH] sudoku solver now solves complex puzzles

---
 src/sudoku-hs/src/Main.hs | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/src/sudoku-hs/src/Main.hs b/src/sudoku-hs/src/Main.hs
index 70574cc..9dc5c4f 100644
--- a/src/sudoku-hs/src/Main.hs
+++ b/src/sudoku-hs/src/Main.hs
@@ -33,14 +33,20 @@ printGrid = putStrLn . unlines . map (unwords . map showCell)
   where showCell = maybe "." show
 
 solve :: Grid -> Maybe Grid
-solve g = case nextCell g of
-  Nothing -> Just g
-  Just (r, c, opts) ->
-    listToMaybe
-      [ result
-      | n <- opts
-      , let g' = updateGrid g r c (Just n)
-      , Just result <- [solve g'] ]
+solve g
+  | isComplete g = Just g
+  | otherwise = case nextCell g of
+      Nothing -> Nothing
+      Just (r, c, opts) ->
+        listToMaybe
+          [ result
+          | n <- opts
+          , let g' = updateGrid g r c (Just n)
+          , Just result <- [solve g']
+          , isComplete result ]
+
+isComplete :: Grid -> Bool
+isComplete = all (notElem Nothing)
 
 nextCell :: Grid -> Maybe (Int, Int, [Int])
 nextCell g =
@@ -62,7 +68,7 @@ getRow :: Int -> Grid -> [Cell]
 getRow r g = g !! r
 
 getCol :: Int -> Grid -> [Cell]
-getCol c g = map (!! c) g
+getCol c = map (!! c)
 
 getBox :: Int -> Int -> Grid -> [Cell]
 getBox r c g =
@@ -85,6 +91,6 @@ main = do
     [filePath] -> do
       grid <- readCSV filePath
       case solve grid of
-        Nothing -> putStrLn "No solution found."
+        Nothing -> putStrLn "No complete solution found."
         Just g  -> printGrid g
     _ -> putStrLn "Usage: sudoku-solver <sudoku.csv>"