57 lines
1.2 KiB
Markdown
57 lines
1.2 KiB
Markdown
---
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title: Breadth-First Search
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---
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## Breadth-First Search
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Let's first define the `Tree` class to be used for the implementation of the Breadth First Search algorithm.
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```python
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class Tree:
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def __init__(self, x):
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self.val = x
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self.left = None
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self.right = None
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```
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The breadth first search algorithm moves from one level to another starting from the root of the tree. We will make use of a `queue` for this.
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```python
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def bfs(root_node):
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queue = [root_node]
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while queue:
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top_element = queue.pop()
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print("Node processed: ",top_element)
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if top_element.left:
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queue.append(top_element.left)
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if top_element.right:
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queue.append(top_element.right)
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```
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We can easily modify the above code to print the level of each node as well.
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```python
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def bfs(root_node):
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queue = [(root_node, 0)]
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while queue:
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top_element, level = queue.pop()
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print("Node processed: {} at level {}".format(top_element, level))
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if top_element.left:
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queue.append((top_element.left, level + 1))
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if top_element.right:
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queue.append((top_element.right, level + 1))
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```
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| Complexity | Time | Space |
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| ----- | ------ | ------ |
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| BFS | n | n |
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