kruskal

class Graph:
def init(self, vertices):
self.V = vertices
self.graph = []
def add_edge(self, u, v, w):
self.graph.append([u, v, w])

def find(self, parent, i):
if parent[i] == i:
return i
return self.find(parent, parent[i])
def apply_union(self, parent, rank, x, y):
xroot = self.find(parent, x)
yroot = self.find(parent, y)
if rank[xroot] < rank[yroot]:
parent[xroot] = yroot
elif rank[xroot] > rank[yroot]:
parent[yroot] = xroot
else:
parent[yroot] = xroot
rank[xroot] += 1

def kruskal_algo(self):
result = []
i, e = 0, 0
self.graph = sorted(self.graph, key=lambda item: item[2])
parent = []
rank = []
for node in range(self.V):
parent.append(node)
rank.append(0)
while e < self.V - 1:
u, v, w = self.graph[i]
i = i + 1
x = self.find(parent, u)
y = self.find(parent, v)
if x != y:
e = e + 1
result.append([u, v, w])
self.apply_union(parent, rank, x, y)
for u, v, weight in result:
print("%d - %d: %d" % (u, v, weight))
g = Graph(4)
g.add_edge(0, 1, 1)
g.add_edge(0, 2, 5)
g.add_edge(0, 3, 2)
g.add_edge(2, 0, 5)
g.add_edge(2, 3, 3)
g.add_edge(3, 2, 3)
g.add_edge(3, 0, 2)
g.kruskal_algo()