forked from amanmehara/programming
-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathDijkstras.py
More file actions
65 lines (48 loc) · 1.9 KB
/
Copy pathDijkstras.py
File metadata and controls
65 lines (48 loc) · 1.9 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
'''
Copyright [2020] [Anoop Bhat]
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
'''
import math
def Dijkstras(graph, start, goal):
unseen_nodes = graph
predecessor = {}
shortest_distance = {}
path = []
infinty = math.inf
for node in unseen_nodes:
shortest_distance[node] = infinty
shortest_distance[start] = 0
while unseen_nodes:
minNode = None
for node in unseen_nodes:
if minNode is None:
minNode = node
elif shortest_distance[node] < shortest_distance[minNode]:
minNode = node
for chilNode,weight in graph[minNode].items():
if weight + shortest_distance[minNode] < shortest_distance[chilNode]:
shortest_distance[chilNode] = weight + shortest_distance[minNode]
predecessor[chilNode] = minNode
unseen_nodes.pop(minNode)
curren_node = goal
while curren_node != start:
try:
path.insert(0,curren_node)
curren_node = predecessor[curren_node]
except KeyError:
print('path not found')
break
path.insert(0,start)
if shortest_distance[goal] != infinty:
print('The shortest distance is ' + str(shortest_distance[goal]))
print('And the path is ' + str(path))
graph = {'a':{'b':10,'c':3},'b':{'c':1,'d':2},'c':{'b':4,'d':8,'e':2},'d':{'e':7},'e':{'d':9}}
Dijkstras(graph, 'a', 'd')