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February 14, 2015 03:18
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Python kruskal algorithm for minimum spanning tree
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import sys | |
from heapq import heappush, heappop | |
class UFSet: | |
def __init__(self, n): | |
self.fa = [i for i in range(n)] | |
def find(self, v): | |
if v != self.fa[v]: | |
self.fa[v] = self.find(self.fa[v]) | |
return self.fa[v] | |
def union(self, a, b): | |
pa = self.find(a) | |
pb = self.find(b) | |
self.fa[pa] = pb | |
def kruscal(Edges, V): | |
ufset = UFSet(V) | |
ret = 0 | |
for w, a, b in Edges: | |
pa, pb = ufset.find(a), ufset.find(b) | |
if pa == pb: | |
continue | |
else: | |
ret += w | |
ufset.union(pa, pb) | |
return ret | |
if __name__ == '__main__': | |
line = sys.stdin.readline() | |
V, E = line.split() | |
V, E = int(V), int(E) | |
Es = [] | |
for i in range(E): | |
line = sys.stdin.readline() | |
a, b, w = line.split() | |
a, b, w = int(a), int(b), int(w) | |
Es.append((w, a, b)) | |
Es.sort() | |
sys.stdout.write(str(kruscal(Es, V)) + '\n') | |
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