110. Balanced Binary Tree

class Solution:
    def isBalanced(self, root: TreeNode) -> bool:
        def get_height(root):
            if not root:
                return 0
            l_ht, r_ht = get_height(root.left), get_height(root.right)
            if l_ht < 0 or r_ht < 0 or abs(l_ht - r_ht) > 1:
                return -1
            return max(l_ht, r_ht) +1
        
        return (get_height(root) >=0)