51 lines
1.2 KiB
Markdown
51 lines
1.2 KiB
Markdown
---
|
|
title: Breadth-First Search
|
|
localeTitle: 广度优先搜索
|
|
---
|
|
## 广度优先搜索
|
|
|
|
让我们首先定义用于实现广度优先搜索算法的`Tree`类。
|
|
|
|
```python
|
|
class Tree:
|
|
def __init__(self, x):
|
|
self.val = x
|
|
self.left = None
|
|
self.right = None
|
|
```
|
|
|
|
广度优先搜索算法从树的根开始从一个级别移动到另一个级别。我们将为此使用`queue` 。
|
|
|
|
```python
|
|
def bfs(root_node):
|
|
queue = [root_node]
|
|
|
|
while queue:
|
|
top_element = queue.pop()
|
|
print("Node processed: ",top_element)
|
|
|
|
if top_element.left:
|
|
queue.append(top_element.left)
|
|
|
|
if top_element.right:
|
|
queue.append(top_element.right)
|
|
```
|
|
|
|
我们可以轻松修改上面的代码来打印每个节点的级别。
|
|
|
|
```python
|
|
def bfs(root_node):
|
|
queue = [(root_node, 0)]
|
|
|
|
while queue:
|
|
top_element, level = queue.pop()
|
|
print("Node processed: {} at level {}".format(top_element, level))
|
|
|
|
if top_element.left:
|
|
queue.append((top_element.left, level + 1))
|
|
|
|
if top_element.right:
|
|
queue.append((top_element.right, level + 1))
|
|
```
|
|
|
|
|复杂性|时间|空间| | ----- | ------ | ------ | | BFS | n | n | |