one-file-projects/spr.py

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Python
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2015-04-22 18:33:54 +02:00
A = "A"
B = "B"
C = "C"
#D = "D"
E = "E"
F = "F"
nodes = [A,B,C,E,F]
edges = {
(A,B,3),
(A,C,4),
# (B,D,5),
(B,E,2),
# (C,D,1),
# (D,E,2),
# (D,F,4),
(E,F,6)
}
def getadjacent(node, edges):
adjacent = set()
for (s,t,l) in edges:
if s == node:
adjacent.add( (t,l) )
elif t == node:
adjacent.add( (s,l) )
return adjacent
def spr(s,t, nodes, edges):
nodes = set(nodes)
m = { s:(0,[s])}
S = set([s])
S2 = set(S)
while S < nodes:
for s in set(S2):
S2.remove( s )
l,p = m[s]
for (ad,sl) in getadjacent(s, edges):
if ad not in S:
m[ad] = (l+sl,p+[ad])
else:
ad_l,_ = m[ad]
if ad_l > l+sl:
m[ad] = (l+sl,p+[ad])
S.add( ad )
S2.add( ad )
return m[t]
print( spr(A,F, nodes, edges) )