Practice dijkstra's algorithm
Getting some practice with Python's heapq module (which I'm unsure if I used correctly) to do a priority-first-traversal of a graph: known as Dijkstra's algorithm.
This commit is contained in:
parent
91811236a5
commit
c010e6d6cf
1 changed files with 26 additions and 0 deletions
26
deepmind/dijkstra.py
Normal file
26
deepmind/dijkstra.py
Normal file
|
@ -0,0 +1,26 @@
|
||||||
|
# Doing a practice implementation of Dijkstra's algorithm: a priority-first
|
||||||
|
# search.
|
||||||
|
from heapq import heappush, heappop
|
||||||
|
|
||||||
|
|
||||||
|
class Node(object):
|
||||||
|
def __init__(self, value, children):
|
||||||
|
self.value = value
|
||||||
|
self.children = children
|
||||||
|
|
||||||
|
|
||||||
|
def shortest_path(a, b):
|
||||||
|
"""Return the shortest path from `a` to `b`."""
|
||||||
|
q = []
|
||||||
|
seen = set()
|
||||||
|
heappush((a.value, a, [a]), q)
|
||||||
|
|
||||||
|
while q:
|
||||||
|
d, node, path = heappop(q)
|
||||||
|
if node == b:
|
||||||
|
return path
|
||||||
|
seen.add(node)
|
||||||
|
for child in node.children:
|
||||||
|
if child not in seen:
|
||||||
|
heappush((d + child.value, child, path + [child]), q)
|
||||||
|
raise Exception("Path between nodes A and B does not exist.")
|
Loading…
Reference in a new issue