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26ffad9d17
* Simplify is_bst.py
* updating DIRECTORY.md
* Update is_bst.py
* Rename is_bst.py to is_sorted.py
* updating DIRECTORY.md
* Update data_structures/binary_tree/is_sorted.py
Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>
---------
Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>
98 lines
3.0 KiB
Python
98 lines
3.0 KiB
Python
"""
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Given the root of a binary tree, determine if it is a valid binary search tree (BST).
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A valid binary search tree is defined as follows:
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- The left subtree of a node contains only nodes with keys less than the node's key.
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- The right subtree of a node contains only nodes with keys greater than the node's key.
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- Both the left and right subtrees must also be binary search trees.
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In effect, a binary tree is a valid BST if its nodes are sorted in ascending order.
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leetcode: https://leetcode.com/problems/validate-binary-search-tree/
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If n is the number of nodes in the tree then:
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Runtime: O(n)
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Space: O(1)
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"""
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from __future__ import annotations
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from collections.abc import Iterator
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from dataclasses import dataclass
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@dataclass
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class Node:
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data: float
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left: Node | None = None
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right: Node | None = None
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def __iter__(self) -> Iterator[float]:
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"""
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>>> root = Node(data=2.1)
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>>> list(root)
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[2.1]
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>>> root.left=Node(data=2.0)
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>>> list(root)
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[2.0, 2.1]
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>>> root.right=Node(data=2.2)
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>>> list(root)
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[2.0, 2.1, 2.2]
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"""
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if self.left:
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yield from self.left
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yield self.data
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if self.right:
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yield from self.right
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@property
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def is_sorted(self) -> bool:
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"""
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>>> Node(data='abc').is_sorted
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True
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>>> Node(data=2,
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... left=Node(data=1.999),
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... right=Node(data=3)).is_sorted
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True
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>>> Node(data=0,
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... left=Node(data=0),
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... right=Node(data=0)).is_sorted
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True
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>>> Node(data=0,
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... left=Node(data=-11),
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... right=Node(data=3)).is_sorted
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True
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>>> Node(data=5,
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... left=Node(data=1),
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... right=Node(data=4, left=Node(data=3))).is_sorted
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False
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>>> Node(data='a',
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... left=Node(data=1),
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... right=Node(data=4, left=Node(data=3))).is_sorted
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Traceback (most recent call last):
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...
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TypeError: '<' not supported between instances of 'str' and 'int'
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>>> Node(data=2,
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... left=Node([]),
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... right=Node(data=4, left=Node(data=3))).is_sorted
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Traceback (most recent call last):
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...
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TypeError: '<' not supported between instances of 'int' and 'list'
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"""
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if self.left and (self.data < self.left.data or not self.left.is_sorted):
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return False
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if self.right and (self.data > self.right.data or not self.right.is_sorted):
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return False
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return True
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if __name__ == "__main__":
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import doctest
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doctest.testmod()
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tree = Node(data=2.1, left=Node(data=2.0), right=Node(data=2.2))
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print(f"Tree {list(tree)} is sorted: {tree.is_sorted = }.")
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assert tree.right
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tree.right.data = 2.0
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print(f"Tree {list(tree)} is sorted: {tree.is_sorted = }.")
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tree.right.data = 2.1
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print(f"Tree {list(tree)} is sorted: {tree.is_sorted = }.")
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