广度优先搜索（BFS）通用实现
广度优先搜索（BFS）的基本实现
LeetCode题目示例
1. 二叉树的层序遍历 (102)
from collections import deque
def bfs(graph, root):
visited = set()
queue = deque([root])
while queue:
vertex = queue.popleft()
print(vertex, end=" ")
if vertex not in visited:
visited.add(vertex)
queue.extend(graph[vertex] - visited)
# 示例图
graph = {
'A' : ['B','C'],
'B' : ['D', 'E'],
'C' : ['F'],
'D' : [],
'E' : ['F'],
'F' : []
}
bfs(graph, 'A') # 从节点'A'开始BFS
# Definition for a binary tree node.
class TreeNode:
def __init__(self, val=0, left=None, right=None):
self.val = val
self.left = left
self.right = right
def levelOrder(root):
if not root:
return []
result, queue = [], deque([root])
while queue:
level_size = len(queue)
current_level = []
for _ in range(level_size):
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