hello-algo/codes/python/chapter_tree/binary_tree_bfs.py

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"""
File: binary_tree_bfs.py
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Created Time: 2022-12-20
Author: a16su (lpluls001@gmail.com)
"""
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 modules import *
from collections import deque
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def level_order(root: TreeNode | None) -> list[int]:
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"""层序遍历"""
# 初始化队列,加入根节点
queue: deque[TreeNode] = deque()
queue.append(root)
# 初始化一个列表,用于保存遍历序列
res: list[int] = []
while queue:
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node: TreeNode = queue.popleft() # 队列出队
res.append(node.val) # 保存节点值
if node.left is not None:
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queue.append(node.left) # 左子节点入队
if node.right is not None:
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queue.append(node.right) # 右子节点入队
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return res
""" Driver Code """
if __name__ == "__main__":
# 初始化二叉树
# 这里借助了一个从数组直接生成二叉树的函数
root: TreeNode = list_to_tree(arr=[1, 2, 3, 4, 5, 6, 7])
print("\n初始化二叉树\n")
print_tree(root)
# 层序遍历
res: list[int] = level_order(root)
print("\n层序遍历的节点打印序列 = ", res)
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assert res == [1, 2, 3, 4, 5, 6, 7]