广度优先搜索 (Breadth-First Search (BFS))

概述

难度：中等 (Medium)
分类：Graph Traversal / 图遍历

广度优先搜索是一种层次遍历算法，先访问所有邻居节点，再向外扩展。

BFS is a level-order traversal algorithm that visits all neighbor nodes first before expanding outward.

算法原理

中文：使用队列，从起点开始，先访问所有邻居入队，再依次处理队列中的节点。

English: Using a queue, start from source, enqueue all neighbors, then process nodes in queue order.

复杂度分析

代码实现

from collections import deque

def bfs(graph, start):
    visited = set()
    queue = deque([start])
    visited.add(start)
    
    while queue:
        node = queue.popleft()
        print(node, end=' ')
        for neighbor in graph[node]:
            if neighbor not in visited:
                visited.add(neighbor)
                queue.append(neighbor)
    return visited

每日练习

1. 完成算法实现
2. 分析算法复杂度
3. 思考：算法的适用场景和局限性

相关阅读：算法专栏

💡 学习建议：算法学习重在理解思想，多写多练是关键。 💡 Learning tip: Algorithm learning is about understanding the core idea. Practice makes perfect.