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* Retranslate the complete English edition from Simplified Chinese * Polish three English explanations after reader-focused review
66 lines
1.6 KiB
Python
66 lines
1.6 KiB
Python
"""
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File: binary_tree_dfs.py
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Created Time: 2022-12-20
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Author: a16su (lpluls001@gmail.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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def pre_order(root: TreeNode | None):
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"""Preorder traversal"""
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if root is None:
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return
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# Visit order: root -> left subtree -> right subtree
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res.append(root.val)
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pre_order(root=root.left)
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pre_order(root=root.right)
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def in_order(root: TreeNode | None):
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"""Inorder traversal"""
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if root is None:
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return
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# Visit order: left subtree -> root -> right subtree
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in_order(root=root.left)
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res.append(root.val)
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in_order(root=root.right)
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def post_order(root: TreeNode | None):
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"""Postorder traversal"""
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if root is None:
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return
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# Visit order: left subtree -> right subtree -> root
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post_order(root=root.left)
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post_order(root=root.right)
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res.append(root.val)
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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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root = list_to_tree(arr=[1, 2, 3, 4, 5, 6, 7])
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print("\nInitialize the binary tree\n")
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print_tree(root)
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# Preorder traversal
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res = []
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pre_order(root)
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print("\nNode sequence from preorder traversal = ", res)
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# Inorder traversal
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res.clear()
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in_order(root)
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print("\nNode sequence from inorder traversal = ", res)
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# Postorder traversal
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res.clear()
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post_order(root)
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print("\nNode sequence from postorder traversal = ", res)
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