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binary_search_tree_iterator.py
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binary_search_tree_iterator.py
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# coding: utf-8
"""
https://leetcode.com/problems/binary-search-tree-iterator/
"""
import itertools
class TreeNode: # pragma: no cover
def __init__(self, val=0, left=None, right=None):
self.val = val
self.left = left
self.right = right
class BSTIterator:
def __init__(self, root: TreeNode):
def inorder_traverse(node):
if not node:
return
yield from inorder_traverse(node.left)
yield node.val
yield from inorder_traverse(node.right)
self.generator = inorder_traverse(root)
def next(self) -> int:
"""
@return the next smallest number
"""
try:
return next(self.generator)
except StopIteration:
return
def hasNext(self) -> bool:
"""
@return whether we have a next smallest number
"""
used_generator, checked_generator = itertools.tee(self.generator)
self.generator = used_generator
try:
next(checked_generator)
except StopIteration:
return False
return True
# Your BSTIterator object will be instantiated and called as such:
# obj = BSTIterator(root)
# param_1 = obj.next()
# param_2 = obj.hasNext()