Trying some overlap logic in Day 1

src/advent_of_code/2023/1.hs

@@ -85,14 +85,40 @@ isNumP2 = flip elem (numberChars ++ numberWords)
 -- Parsing for question
 --
 
-numberWords :: [String]
+letterChars :: String
-numberWords = ["zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"]
+letterChars = ['a'..'z']
 
 numberChars :: [String]
 numberChars = map show [0..9]
 
-letterChars :: String
+numberWords :: [String]
-letterChars = ['a'..'z']
+numberWords = ["zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"]
+
+overlapsSpec :: [(String, String)]
+overlapsSpec =
+  [ ("zero" , "one"  )
+  , ("one"  , "eight")
+  , ("two"  , "one"  )
+  , ("three", "eight")
+  , ("five" , "eight")
+  , ("seven", "nine" )
+  , ("eight", "two"  )
+  , ("eight", "three")
+  , ("nine" , "eight")
+  ]
+
+overlapsDerived :: [(String, [String])]
+overlapsDerived = zip numberWords $ map findOverlaps numberWords
+
+findOverlaps :: String -> [String]
+findOverlaps str = filter (\s -> last str == head s) numberWords
+
+combineOverlaps :: (String, [String]) -> [String]
+combineOverlaps (numStr, []       ) = []
+combineOverlaps (numStr, over:laps) = (numStr ++ tail over) : combineOverlaps (numStr, laps)
+
+overlaps :: [String]
+overlaps = filter (/= "") $ concatMap combineOverlaps overlapsDerived
 
 parseNumberWords :: ReadP String
 parseNumberWords = choice $ map string numberWords