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data LeftistHeap a = E | T Int a (LeftistHeap a) (LeftistHeap a) deriving (Show)

rank E = 0
rank (T r _ _ _) = r

makeT x a b = if rank a >= rank b then T (rank b + 1) x a b
               else T (rank a + 1) x b a

empty = E
isEmpty E = True
isEmpty _ = False

insert x = merge (T 1 x E E)

merge h E = h
merge E h = h
merge h1@(T _ x a1 b1) h2@(T _ y a2 b2) =
    if x <= y then makeT x a1 (merge b1 h2)
    else makeT y a2 (merge b1 h2)

findMin E = error "empty heap"
findMin (T _ x a b) = x

deleteMin E = error "empty heap"
deleteMin (T _ x a b) = merge a b