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67 lines
1.6 KiB
Python
67 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, os.path as osp
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sys.path.append(osp.dirname(osp.dirname(osp.abspath(__file__))))
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from include import *
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res = []
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""" 前序遍历 """
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def pre_order(root: Optional[TreeNode]):
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if root is None:
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return
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# 访问优先级：根结点 -> 左子树 -> 右子树
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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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""" 中序遍历 """
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def in_order(root: Optional[TreeNode]):
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if root is None:
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return
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# 访问优先级：左子树 -> 根结点 -> 右子树
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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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""" 后序遍历 """
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def post_order(root: Optional[TreeNode]):
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if root is None:
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return
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# 访问优先级：左子树 -> 右子树 -> 根结点
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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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# 初始化二叉树
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# 这里借助了一个从数组直接生成二叉树的函数
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root = list_to_tree(arr=[1, 2, 3, 4, 5, 6, 7])
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print("\n初始化二叉树\n")
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print_tree(root)
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# 前序遍历
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res.clear()
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pre_order(root)
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print("\n前序遍历的结点打印序列 = ", res)
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assert res == [1, 2, 4, 5, 3, 6, 7]
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# 中序遍历
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res.clear()
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in_order(root)
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print("\n中序遍历的结点打印序列 = ", res)
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assert res == [4, 2, 5, 1, 6, 3, 7]
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# 后序遍历
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res.clear()
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post_order(root)
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print("\n后序遍历的结点打印序列 = ", res)
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assert res == [4, 5, 2, 6, 7, 3, 1]
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