def dijkstra(graph, start):
distance = {}
for node in graph:
distance[node] = maxint # a very large number used for "infinity"
distance[start] = 0
previous = {}
previous[start] = 'nil'
q = priorityQueue.makeQueue(distance) # priority queue using distance-values as keys
while len(q) > 0:
(value, u) = priorityQueue.deletemin(q)
for edge in graph[u]:
l = length(edge)
v = otherEnd(edge)
if distance[v] > distance[u] + l:
distance[v] = distance[u] + l
previous[v] = u
priorityQueue.decreasekey(q, v, distance[v])
print "Decreasekey for", v, "to", distance[v]
#print "Dijkstra from", start, ":"
#print "Distances:", distance
#print "Previous:", previous
return distance
import pq q = [(4, "a"), (5, "b"), (3, "c")] print q m = pq.deletemin(q) print m, q pq.decreasekey(q, "b", 2) print q
