forked from keon/algorithms
-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathclone_graph.py
More file actions
131 lines (104 loc) · 3.66 KB
/
clone_graph.py
File metadata and controls
131 lines (104 loc) · 3.66 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
"""
Clone an Undirected Graph
Each node contains a label and a list of its neighbours. Three strategies
are provided: BFS-based, iterative DFS, and recursive DFS.
Reference: https://leetcode.com/problems/clone-graph/
Complexity:
Time: O(V + E)
Space: O(V)
"""
from __future__ import annotations
import collections
class UndirectedGraphNode:
"""A node in an undirected graph."""
def __init__(self, label: int) -> None:
self.label = label
self.neighbors: list[UndirectedGraphNode] = []
def shallow_copy(self) -> UndirectedGraphNode:
"""Return a copy of this node without neighbours.
Returns:
A new node with the same label.
"""
return UndirectedGraphNode(self.label)
def add_neighbor(self, node: UndirectedGraphNode) -> None:
"""Append *node* to the neighbour list.
Args:
node: Neighbour to add.
"""
self.neighbors.append(node)
def clone_graph1(node: UndirectedGraphNode | None) -> UndirectedGraphNode | None:
"""Clone a graph using BFS.
Args:
node: Any node in the original graph.
Returns:
The corresponding node in the cloned graph, or None.
"""
if not node:
return None
node_copy = node.shallow_copy()
dic: dict[UndirectedGraphNode, UndirectedGraphNode] = {node: node_copy}
queue: collections.deque[UndirectedGraphNode] = collections.deque([node])
while queue:
node = queue.popleft()
for neighbor in node.neighbors:
if neighbor not in dic:
neighbor_copy = neighbor.shallow_copy()
dic[neighbor] = neighbor_copy
dic[node].add_neighbor(neighbor_copy)
queue.append(neighbor)
else:
dic[node].add_neighbor(dic[neighbor])
return node_copy
def clone_graph2(node: UndirectedGraphNode | None) -> UndirectedGraphNode | None:
"""Clone a graph using iterative DFS.
Args:
node: Any node in the original graph.
Returns:
The corresponding node in the cloned graph, or None.
"""
if not node:
return None
node_copy = node.shallow_copy()
dic: dict[UndirectedGraphNode, UndirectedGraphNode] = {node: node_copy}
stack = [node]
while stack:
node = stack.pop()
for neighbor in node.neighbors:
if neighbor not in dic:
neighbor_copy = neighbor.shallow_copy()
dic[neighbor] = neighbor_copy
dic[node].add_neighbor(neighbor_copy)
stack.append(neighbor)
else:
dic[node].add_neighbor(dic[neighbor])
return node_copy
def clone_graph(node: UndirectedGraphNode | None) -> UndirectedGraphNode | None:
"""Clone a graph using recursive DFS.
Args:
node: Any node in the original graph.
Returns:
The corresponding node in the cloned graph, or None.
"""
if not node:
return None
node_copy = node.shallow_copy()
dic: dict[UndirectedGraphNode, UndirectedGraphNode] = {node: node_copy}
_dfs(node, dic)
return node_copy
def _dfs(
node: UndirectedGraphNode,
dic: dict[UndirectedGraphNode, UndirectedGraphNode],
) -> None:
"""Recursively clone neighbours into *dic*.
Args:
node: Current node being cloned.
dic: Mapping from original nodes to their clones.
"""
for neighbor in node.neighbors:
if neighbor not in dic:
neighbor_copy = neighbor.shallow_copy()
dic[neighbor] = neighbor_copy
dic[node].add_neighbor(neighbor_copy)
_dfs(neighbor, dic)
else:
dic[node].add_neighbor(dic[neighbor])