Haskll，高度平衡檢查

Question

有沒有辦法將其轉換，以便根據身高檢查平衡？ （假設這就是問題所在。）

size :: Tree a -> Int 
size (Leaf n) = 1 
size (Node x z) = size x + size z + 1 

isBalanced :: Tree a -> Bool 
isBalanced (Leaf _) = True 
isBalanced (Node l r) = 
    let diff = abs (size l - size r) in 
    diff <= 1 && isBalanced l && isBalanced r 

例如：

isBalanced (Node (Node (Leaf 1)(Leaf 3)) (Leaf 2))) = True (Currently returns False) 
isBalanced (Node (Node (Leaf 1)(Node (Leaf 1)(Leaf 3))) (Leaf 2))) = False 

Answer 1

似乎size計數節點的總數。如果要計算（最大值）的高度，而不是，你想是這樣的：

height :: Tree x -> Int 
height (Leaf _) = 1 
height (Node x y) = 1 + (height x `max` height y) 

如果你只是用height取代size，該isBalanced代碼應該像以前一樣工作。

這是否修復您的問題還有待觀察，當然，...