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ALGORITHM FOR INTELLIGENT SYSTEMS
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LAB – 3: Searching in AI
Breadth First Traversal (BFS) for a Graph Code:
Python3 Program to print BFS traversal
from a given source vertex. BFS(int s)
traverses vertices reachable from s.
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)
self.graph = defaultdict(list)
function to add an edge to graph
def addEdge(self, u, v): self.graph[u].append(v)
A function used by DFS
def DFSUtil(self, v, visited):
Mark the current node as visited
and print it
visited.add(v) print(v, end=' ')
Recur for all the vertices
adjacent to this vertex
for neighbour in self.graph[v]: if neighbour not in visited: self.DFSUtil(neighbour, visited)
The function to do DFS traversal. It uses
recursive DFSUtil()
def DFS(self, v):
Create a set to store visited vertices
visited = set()
Call the recursive helper function
to print DFS traversal
self.DFSUtil(v, visited)
Driver's code
Create a graph given
in the above diagram
if name == "main":
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 DFS from (starting from vertex 2)")
Function call
g.DFS(2) Result: Iterative Depth First Traversal (Iterative DFS) for a Graph Code:
An Iterative Python program to do DFS traversal from
a given source vertex. DFS(int s) traverses vertices
reachable from s.
Get all adjacent vertices of the popped vertex s
If a adjacent has not been visited, then push it
to the stack.
for node in self.adj[s]: if (not visited[node]): stack.append(node)
Driver program to test methods of graph class
g = Graph(5); # Total 5 vertices in graph g.addEdge(1, 0); g.addEdge(0, 2); g.addEdge(2, 1); g.addEdge(0, 3); g.addEdge(1, 4); print("Following is Depth First Traversal") g.DFS(0) Result:
