common-substring.hs

-- from hackerrank.com
-- https://www.hackerrank.com/challenges/common-child

-- define child to be a (not necessarily continuous) substring
-- find the longest sub-child of two strings

import Control.Monad
import Debug.Trace
import System.Environment
import System.IO

-- haskell will not do memoization for you
solve :: (Ord a) => [a] -> [a] -> Int
solve [] _ = 0
solve _ [] = 0
solve (x:xs) (y:ys) = 
  if x == y 
    then solve xs ys + 1
    else solve xs (y:ys) `max` solve (x:xs) ys

{-
-- sequential version
iterHelper :: (Ord a) => [a] -> a -> [Int] -> Int -> [Int]
-- assert : length xs == length ls
iterHelper [] _ _ _ = []
iterHelper (x:xs) y (ol:l:ls) ll = d : iterHelper xs y (l:ls) d
  where d = if y == x then ol + 1 else max l ll
iterHelper _ _ (_:_) _ = error "IterList exhausted"
-}

-- turn iterHelper to a tail-call version
iterHelper' :: (Ord a) => [a] -> a -> [Int] -> Int -> [Int] -> [Int]
iterHelper' [] _ _ _ res = reverse res
iterHelper' (x:xs) y (ol:l:ls) ll res = iterHelper' xs y (l:ls) d (d:res)
  where d = if y == x then ol + 1 else max l ll
iterHelper' _ _ (_:_) _ _ = error "IterList exhausted"

ccHelper :: (Ord a) => [a] -> [a] -> [Int] -> Int
ccHelper xs [] ls = head $ reverse ls
ccHelper xs (y:ys) ls = ccHelper xs ys $! iterHelper' xs y (0:ls) 0 []

commonChild :: (Ord a) => [a] -> [a] -> Int
commonChild xs ys = ccHelper xs ys $ replicate (length xs) 0

main = do
  [path] <- getArgs
  h <- openFile path ReadMode
  [x, y] <- replicateM 2 (hGetLine h)
  putStrLn . show $ commonChild x y

--main = print $ iterHelper "shabi" 'i' (0:[0,0,0,0,0]) 0

input-large.txt

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

input.txt

APMCTKBUKYRGZPAUVZEBVUXRGDVITOYXWQWRVCSXESMEHQLHPDJQWETAWQVSBRRNRRFDLFTRXOTKQHFTYAZSGBORDNAMUAJTPVOKERLVOLEALDQQLUDCUIRXJHQEZBRWYPFJXNTPELEZHNJILIZVZLYQJDFYSYQNRFFAOYXHQBQVRLFDIIOGWKQIZGVELYOUKZBKMHVYGIKIPSEMWSCWYOJTHOQKMLBAIZYNAKYNCXKDTTESODDAEAHKCDHCJYAHERACMLYQHXIRDFUSRTZDNVHSYFKCSPPYSLHOGIBTNUJTZQWVTHKUNDNWZADMATSUXEISCACQNQXIHNTXGCZUGIGBDONYTUXAXFINAYGZJVDCTZCWPGFNQDPERUCNJUXIFDSQHULYPZRNUOKMLMMQAJMLKCHJMEFJVRYZIPFQOBSDPAITHGMNKROCWJEGESCGOIUOQHOYUEQNPJPBMCNRZUHOSQNSUNCSTVQVWFGMUFJZGMEUVUPH
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

output-large.txt

1417

output.txt

155

Substr2.hs

import Control.Monad
import qualified Data.ByteString as B
import qualified Data.Vector.Unboxed as U
import Data.Word
import System.Environment
import System.IO

iterHelper :: B.ByteString -> Word8 ->
              U.Vector Int -> Int -> 
              U.Vector Int -> U.Vector Int
iterHelper xs y ls ll res = case B.null xs of
  True -> U.reverse res
  _ | U.length ls >= 2 -> let x = B.head xs
                              xs' = B.tail xs
                              ol = U.head ls
                              l = ls U.! 1
                              ls' = U.tail ls
                              d = if y == x
                                    then ol + 1
                                    else max l ll
                              res' = d `U.cons` res
                           in iterHelper xs' y ls' d res'
    | otherwise -> error "iterHelper: exhausted"


ccHelper :: B.ByteString -> B.ByteString -> U.Vector Int -> Int
ccHelper xs ys ls = case B.null ys of
  True -> U.head $ U.reverse ls
  False -> ccHelper xs (B.tail ys) $! iterHelper xs (B.head ys)
    (0 `U.cons` ls) 0 U.empty

commonChild :: B.ByteString -> B.ByteString -> Int
commonChild xs ys = ccHelper xs ys $! U.replicate (B.length xs) 0

main = do
  [path] <- getArgs
  h <- openFile path ReadMode
  [x, y] <- replicateM 2 (B.hGetLine h)
  putStrLn . show $ commonChild x y