173.py

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sample 72 ms submission
# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class BSTIterator:

    def __init__(self, root: TreeNode):
        self.stack = []
        while root:
            self.stack.append(root)
            root = root.left
            
    def next(self) -> int:
        """
        @return the next smallest number
        """
        node = self.stack.pop()
        x = node.right
        while x:
            self.stack.append(x)
            x = x.left
        return node.val

    def hasNext(self) -> bool:
        """
        @return whether we have a next smallest number
        """
        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()
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sample 19496 kb submission
# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class BSTIterator:

    def __init__(self, root: TreeNode):
        self.stack = []
        self.traverse(root)
    
    def traverse(self, root):
        if root:
            self.traverse(root.left)
            self.stack.append(root.val)
            self.traverse(root.right)
        self.stack.sort()

    def next(self) -> int:
        """
        @return the next smallest number
        """
        return self.stack.pop(0)
        

    def hasNext(self) -> bool:
        """
        @return whether we have a next smallest number
        """
        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()
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