Submission #448982

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Source Code Expand

main = getLine >>= main' . read . head . words
    where
        main' n = getContents >>= print . solve n . map (map read . words) . lines

solve :: Int -> [[Int]] -> Int
solve n ys = foldl (\acc x -> max acc $ check (getCnd cnds x) cnds) 0 [1..n]
    where
        cnds = foldr ff [] [1..n]
        ff x acc = (x, foldl ff' [] ys) : acc
            where
                ff' acc [a, b]
                    | a == x = b : acc
                    | b == x = a : acc
                    | otherwise = acc

check :: [Int] -> [(Int, [Int])] -> Int
check [] _ = 1
check ys cnds = foldl (\acc y -> max acc $ check (elems y ys $ getCnd cnds y) cnds) 0 ys + 1
    where
        elems x xs = filter (\y -> y /= x && elem y xs)

getCnd :: [(Int, [Int])] -> Int -> [Int]
getCnd cnds = snd . (cnds !!) . pred

Submission Info

Judge Result