# 99 questions/Solutions/82

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< 99 questions | Solutions

Brute-force search from the source, using list comprehension:

```
import Data.List (partition)
cycle' :: Int -> [(Int, Int)] -> [ [Int] ]
cycle' n g = search [[n]] []
where search [] result = result
search cur result = search (go active) (arrive ++ result)
where split = partition end cur
end s = (last s == n) && (length s /= 1)
active = snd split
arrive = fst split
go ls = [ x ++ [snd y] | x <- ls, y <- g, last x == fst y, not (snd y `elem` tail x)]
```

another approach using list as monad

```
cycles :: (Eq a) => a -> [Arc a] -> [[a]]
cycles _ [] = []
cycles start arcs =
map (map fst) $ aux start []
where
aux current pathSoFar =
let nextEdges = filter ((== current) . fst) arcs
notCyclic = not . (\(_,t) -> (elem t $ map snd pathSoFar))
noCycles = filter notCyclic nextEdges
in noCycles >>= \(f,t) -> do
if (t == start) then return $ pathSoFar ++ (f,t):[(t,t)]
else aux t (pathSoFar ++ [(f,t)])
```