Union find algo.py

from collections import defaultdict



class Graph:

    def __init__(self, vertices):
        self.V = vertices
        self.graph = defaultdict(list)


    def addEdge(self, u, v):
        self.graph[u].append(v)


    def find_parent(self, parent, i):
        if parent[i] == -1:
            return i
        if parent[i] != -1:
            return self.find_parent(parent, parent[i])


    def union(self, parent, x, y):
        parent[x] = y


    def isCyclic(self):


        parent = [-1] * (self.V)


        for i in self.graph:
            for j in self.graph[i]:
                x = self.find_parent(parent, i)
                y = self.find_parent(parent, j)
                if x == y:
                    return True
                self.union(parent, x, y)

g = Graph(3)
g.addEdge(0, 1)
g.addEdge(1, 2)
g.addEdge(2, 0)

if g.isCyclic():
    print("Graph contains cycle")
else:
    print("Graph does not contain cycle ")