Created
December 7, 2018 08:29
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DFS implements using Python
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{ | |
"cells": [ | |
{ | |
"cell_type": "code", | |
"execution_count": 1, | |
"metadata": {}, | |
"outputs": [], | |
"source": [ | |
"class Node:\n", | |
" \n", | |
" def __init__(self, name):\n", | |
" self.name = name\n", | |
" self.visited = False\n", | |
" self.neighbors = []\n", | |
" self.predecessor = None # use in shortest path\n", | |
" \n", | |
" def __repr__(self):\n", | |
" return 'Node(name={})'.format(self.name)" | |
] | |
}, | |
{ | |
"cell_type": "code", | |
"execution_count": 2, | |
"metadata": {}, | |
"outputs": [], | |
"source": [ | |
"class DFS:\n", | |
" \"\"\"\n", | |
" For BFS, use queue; For DFS, use stack / recursion(os stack)\n", | |
" \"\"\"\n", | |
" def __init__(self, start):\n", | |
" self.start = start\n", | |
" \n", | |
" def traversal(self):\n", | |
" interface = self.stack()\n", | |
" interface(self.start)\n", | |
" return self.result\n", | |
" \n", | |
" def stack(self):\n", | |
" self.result = []\n", | |
" def interface(node):\n", | |
" self.result.append(node) \n", | |
" node.visited = True\n", | |
" for n in node.neighbors:\n", | |
" if not n.visited:\n", | |
" interface(n) \n", | |
" return interface" | |
] | |
}, | |
{ | |
"cell_type": "markdown", | |
"metadata": {}, | |
"source": [ | |
"![image](https://storage.googleapis.com/ssivart/super9-blog/level-order-traversal.png)\n", | |
"[圖片來源](http://alrightchiu.github.io/SecondRound/graph-breadth-first-searchbfsguang-du-you-xian-sou-xun.html)" | |
] | |
}, | |
{ | |
"cell_type": "code", | |
"execution_count": 3, | |
"metadata": {}, | |
"outputs": [], | |
"source": [ | |
"na = Node('A')\n", | |
"nb = Node('B')\n", | |
"nc = Node('C')\n", | |
"nd = Node('D')\n", | |
"ne = Node('E')\n", | |
"nf = Node('F')\n", | |
"\n", | |
"na.neighbors = [nb, nc]\n", | |
"nb.neighbors = [nd, ne]\n", | |
"nc.neighbors = [nf]" | |
] | |
}, | |
{ | |
"cell_type": "code", | |
"execution_count": 4, | |
"metadata": {}, | |
"outputs": [], | |
"source": [ | |
"dfs = DFS(na)" | |
] | |
}, | |
{ | |
"cell_type": "code", | |
"execution_count": 5, | |
"metadata": {}, | |
"outputs": [ | |
{ | |
"name": "stdout", | |
"output_type": "stream", | |
"text": [ | |
"Node(name=A)\n", | |
"Node(name=B)\n", | |
"Node(name=D)\n", | |
"Node(name=E)\n", | |
"Node(name=C)\n", | |
"Node(name=F)\n" | |
] | |
} | |
], | |
"source": [ | |
"for node in dfs.traversal():\n", | |
" print(node)" | |
] | |
} | |
], | |
"metadata": { | |
"kernelspec": { | |
"display_name": "Python 3", | |
"language": "python", | |
"name": "python3" | |
}, | |
"language_info": { | |
"codemirror_mode": { | |
"name": "ipython", | |
"version": 3 | |
}, | |
"file_extension": ".py", | |
"mimetype": "text/x-python", | |
"name": "python", | |
"nbconvert_exporter": "python", | |
"pygments_lexer": "ipython3", | |
"version": "3.5.2" | |
} | |
}, | |
"nbformat": 4, | |
"nbformat_minor": 2 | |
} |
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