wangbj

revdigits x  = go x 0
  where go k r
          | k == 0 = r
          | otherwise = go d (10*r+m)
            where (d, m) = k `quotRem` 10

isPalin x = id x == revdigits x

wangbj

struct ListNode* uncons (struct ListNode* xxs, struct ListNode** xs)
{
        struct ListNode* x = xxs;

        if (xxs) {
                *xs = xxs -> next;
                x -> next = NULL;
        }

        return x;

wangbj

g = foldr (.) id chain
  where chain = replicate 1000000 succ

wangbj

static bool cache[1024][1024];

class Solution {
public:
  std::string longestPalindrome(std::string s) {
    int sz = (int)s.size();
    if (sz == 0) return s;
    int start = 0, len = 1;
    
    memset(cache, 0, sizeof(cache));

wangbj

{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE DataKinds #-}

data Nat = Z | Succ Nat
               deriving Show

data Vec :: (* -> Nat -> *) where
  Nil :: Vec a Z

wangbj

import qualified Data.ByteString.Char8 as C
import Data.Maybe
import Text.Printf

readPrice = fromJust . readPrice_
  where readPrice_ s = C.readInt s >>= \(x, s1) -> 
          C.uncons s1 >>= \(c, s2) ->
          case c of
           '.' -> C.readInt s2 >>= \(y, s3) -> return (x*100+y)
           _ -> Nothing

wangbj

{-# LANGUAGE ViewPatterns #-}

import qualified Data.Sequence as Seq
import Data.Sequence(Seq)

lastr :: Seq a -> Maybe a
lastr (Seq.viewr -> Seq.EmptyR) = Nothing
lastr (Seq.viewr -> s Seq.:> x) = Just x

wangbj

{-# LANGUAGE PatternSynonyms #-}

import Foreign.C

newtype Mode = MkMode {unMode :: CInt }

pattern Mode0 = MkMode 0
pattern Mode1 = MkMode 1

wangbj

showIntBase2 = reverse . concatMap show . un 
  where un = unfoldr go
        go = uncurry (*>) . (&&&) (guard . (>0)) (Just . swap . (`quotRem` 2))        

-- > showIntBase2 12
-- "1100"

wangbj

data Tree a = Leaf | Branch a !(Tree a) !(Tree a)

inOrder g Leaf = mempty
inOrder g (Branch a l r) = g a <> inOrder g l <> inOrder g r

instance Foldable Tree where
  foldMap g = inOrder g

treeSum :: Tree Integer -> Integer
treeSum = getSum . foldMap Sum