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* Retranslate the complete English edition from Simplified Chinese * Polish three English explanations after reader-focused review
120 lines
3.5 KiB
Python
120 lines
3.5 KiB
Python
"""
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File: array_binary_tree.py
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Created Time: 2023-07-19
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Author: krahets (krahets@163.com)
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"""
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import sys
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from pathlib import Path
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sys.path.append(str(Path(__file__).parent.parent))
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from modules import TreeNode, list_to_tree, print_tree
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class ArrayBinaryTree:
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"""Binary tree class using an array representation"""
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def __init__(self, arr: list[int | None]):
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"""Constructor"""
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self._tree = list(arr)
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def size(self):
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"""Length of the backing list"""
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return len(self._tree)
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def val(self, i: int) -> int | None:
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"""Get the value of the node at index i"""
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# If the index is out of bounds, return None to represent an empty position
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if i < 0 or i >= self.size():
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return None
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return self._tree[i]
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def left(self, i: int) -> int | None:
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"""Get the left child index of the node at index i"""
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return 2 * i + 1
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def right(self, i: int) -> int | None:
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"""Get the right child index of the node at index i"""
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return 2 * i + 2
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def parent(self, i: int) -> int | None:
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"""Get the parent index of the node at index i"""
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return (i - 1) // 2
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def level_order(self) -> list[int]:
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"""Level-order traversal"""
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self.res = []
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# Traverse the array directly
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for i in range(self.size()):
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if self.val(i) is not None:
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self.res.append(self.val(i))
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return self.res
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def dfs(self, i: int, order: str):
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"""Depth-first traversal"""
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if self.val(i) is None:
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return
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# Preorder traversal
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if order == "pre":
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self.res.append(self.val(i))
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self.dfs(self.left(i), order)
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# Inorder traversal
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if order == "in":
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self.res.append(self.val(i))
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self.dfs(self.right(i), order)
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# Postorder traversal
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if order == "post":
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self.res.append(self.val(i))
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def pre_order(self) -> list[int]:
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"""Preorder traversal"""
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self.res = []
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self.dfs(0, order="pre")
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return self.res
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def in_order(self) -> list[int]:
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"""Inorder traversal"""
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self.res = []
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self.dfs(0, order="in")
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return self.res
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def post_order(self) -> list[int]:
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"""Postorder traversal"""
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self.res = []
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self.dfs(0, order="post")
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return self.res
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"""Driver code"""
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if __name__ == "__main__":
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# Initialize the binary tree
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# Use a helper function that builds a binary tree directly from an array
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arr = [1, 2, 3, 4, None, 6, 7, 8, 9, None, None, 12, None, None, 15]
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root = list_to_tree(arr)
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print("\nInitialize the binary tree\n")
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print("Array representation of the binary tree:")
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print(arr)
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print("Linked representation of the binary tree:")
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print_tree(root)
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# Binary tree class using an array representation
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abt = ArrayBinaryTree(arr)
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# Access a node
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i = 1
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l, r, p = abt.left(i), abt.right(i), abt.parent(i)
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print(f"\nCurrent node index: {i}, value: {abt.val(i)}")
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print(f"Left child index: {l}, value: {abt.val(l)}")
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print(f"Right child index: {r}, value: {abt.val(r)}")
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print(f"Parent index: {p}, value: {abt.val(p)}")
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# Traverse the tree
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res = abt.level_order()
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print("\nLevel-order traversal:", res)
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res = abt.pre_order()
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print("Preorder traversal:", res)
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res = abt.in_order()
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print("Inorder traversal:", res)
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res = abt.post_order()
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print("Postorder traversal:", res)
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