Question

from collections import defaultdict

  

# This class represents a directed graph using

# adjacency list representation

class Graph:

  

    # Constructor

    def __init__(self):

  

        # default dictionary to store graph

        self.graph = defaultdict(list)

  

    # function to add an edge to graph

    def addEdge(self,u,v):

        self.graph[u].append(v)

  

    # Function to print a BFS of graph

    def BFS(self, s):

  

        # Mark all the vertices as not visited

        visited = [False] * (len(self.graph))

  

        # Create a queue for BFS

        queue = []

  

        # Mark the source node as

        # visited and enqueue it

        queue.append(s)

        visited[s] = True

  

        while queue:

  

            # Dequeue a vertex from

            # queue and print it

            s = queue.pop(0)

            print (s, end = " ")

  

            # Get all adjacent vertices of the

            # dequeued vertex s. If a adjacent

            # has not been visited, then mark it

            # visited and enqueue it

            for i in self.graph[s]:

                if visited[i] == False:

                    queue.append(i)

                    visited[i] = True

  

# Driver code

  

# Create a graph given in

# the above diagram

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 ("Following is Breadth First Traversal"

                  " (starting from vertex 2)")

g.BFS(2)

The above given code gives Breadth First Traversal for a given graph.

2. Modify the code in such a way that once the traversal reaches the goal the search terminates.

  

           

Note: Write separate python program for question.

Answer 1

In case of any queries, please revert back.

You just need to add 2 lines of code in this question and just modify the parameters of BFS Function :-

The whole code remains same. Here is the BFS function :-

==================== CODE BELOW ==========================

from collections import defaultdict

class Graph:
def __init__(self):
self.graph = defaultdict(list)

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

def BFS(self, s,goal):
visited = [False] * (len(self.graph))
queue = []
queue.append(s)
visited[s] = True
while queue:
s = queue.pop(0)
print (s, end = " ")
# Added part, We dont need to mark further vertice, if we find the goal
if s==goal:
break;
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 ("Following is Breadth First Traversal")
#Modify the BFS function as (start,goal)
g.BFS(2,3)

============================ SCREENSHOTS BELOW ======================