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64 lines
2 KiB
Python
64 lines
2 KiB
Python
"""
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File: binary_tree.py
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Created Time: 2021-12-11
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Author: Krahets (krahets@163.com)
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"""
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import collections
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from typing import List, Deque, Optional
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class TreeNode:
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""" Definition for a binary tree node """
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def __init__(self, val: int = 0, left: Optional['TreeNode'] = None, right: Optional['TreeNode'] = None):
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self.val: int = val # 结点值
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self.height: int = 0 # 结点高度
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self.left: Optional[TreeNode] = left # 左子结点引用
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self.right: Optional[TreeNode] = right # 右子结点引用
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def list_to_tree(arr: List[int]) -> Optional[TreeNode]:
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""" Generate a binary tree with a list """
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if not arr:
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return None
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i: int = 0
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root = TreeNode(arr[0])
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queue: Deque[TreeNode] = collections.deque([root])
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while queue:
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node: TreeNode = queue.popleft()
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i += 1
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if i >= len(arr): break
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if arr[i] != None:
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node.left = TreeNode(arr[i])
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queue.append(node.left)
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i += 1
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if i >= len(arr): break
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if arr[i] != None:
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node.right = TreeNode(arr[i])
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queue.append(node.right)
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return root
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def tree_to_list(root: Optional[TreeNode]) -> List[int]:
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""" Serialize a tree into an array """
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if not root: return []
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queue: Deque[TreeNode] = collections.deque()
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queue.append(root)
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res: List[int] = []
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while queue:
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node: Optional[TreeNode] = queue.popleft()
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if node:
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res.append(node.val)
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queue.append(node.left)
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queue.append(node.right)
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else: res.append(None)
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return res
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def get_tree_node(root: Optional[TreeNode], val: int) -> Optional[TreeNode]:
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""" Get a tree node with specific value in a binary tree """
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if not root:
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return
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if root.val == val:
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return root
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left: Optional[TreeNode] = get_tree_node(root.left, val)
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right: Optional[TreeNode] = get_tree_node(root.right, val)
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return left if left else right
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