BFS.py

from collections import defaultdict 
  
class Graph: 
  
    # Constructor 
    def __init__(self): 
        self.graph = defaultdict(list) 
 
    def addEdge(self,u,v): 
        self.graph[u].append(v) 
  
    def BFS(self, s): 
  
        visited = [False] * (len(self.graph)) 
  
        queue = [] 
        queue.append(s) 
        visited[s] = True
  
        while queue: 
            s = queue.pop(0) 
            print (s, end = " ") 
            for i in self.graph[s]: 
                if visited[i] == False: 
                    queue.append(i) 
                    visited[i] = True
  
 g = Graph() 
g.addEdge(0, 1) 
g.addEdge(0, 2) 
g.addEdge(1, 2) 
g.addEdge(2, 0) 
g.addEdge(2, 3) 
g.addEdge(3, 3) 
  
print ("BFS"+ " (starting from vertex 1)") 
g.BFS(1)