Graph implementation on adjacency lists

[SHREENIDHI03-CSBS]

class Graph:

Initialize graph with an option to set it as directed or undirected

def __init__(self, directed=False):
    # Initialize an empty dictionary to store the graph
    self.graph = {}
    # Set the graph as directed or undirected based on the parameter
    self.directed = directed

def addVertex(self, vertex):
    # If the vertex is not already in the graph, add it
    if vertex not in self.graph:
        self.graph[vertex] = []

def addEdge(self, source, destination):
    # Add source and destination vertices if not present
    self.addVertex(source)
    self.addVertex(destination)
    # Add the edge from source to destination
    self.graph[source].append(destination)
    # If the graph is undirected, add the reverse edge (destination to source)
    if not self.directed:
        self.graph[destination].append(source)

def displayGraph(self):
    # Display the graph in adjacency list format
    for vertex in self.graph:
        print(f"{vertex} -> {self.graph[vertex]}")

Creating an undirected graph (default)

G1 = Graph() G1.addEdge('A', 'B') G1.addEdge('A', 'D') G1.addEdge('A', 'C') G1.addEdge('A', 'E') G1.addEdge('B', 'C') G1.addEdge('C', 'E') G1.addEdge('C', 'D') G1.addEdge('D', 'E')

print("Undirected Graph:") G1.displayGraph()

Creating a directed graph

G2 = Graph(directed=True) G2.addEdge('A', 'B') G2.addEdge('A', 'C') G2.addEdge('B', 'D') G2.addEdge('C', 'D')

print("\nDirected Graph:") G2.displayGraph()