# Definition for a binary tree node. # class TreeNode(object): # def __init__(self, x): # self.val = x # self.left = None # self.right = None class BSTIterator(object): def __init__(self, root): self.stack = [] while root: self.stack.append(root) root = root.left def next(self): node = self.stack.pop() r = node.right while r: self.stack.append(r) r = r.left return node.val def hasNext(self): return len(self.stack)!=0 # Your BSTIterator object will be instantiated and called as such: # obj = BSTIterator(root) # param_1 = obj.next() # param_2 = obj.hasNext()