Added a conditional check for unreachable vertices by replacing infinity

[simran0963]

Problem

• The Dijkstra Algorithm had an issue with checking unreachable vertices

Solution

• Added a conditional check which looks out for unreachable vertices.

Changes proposed in this Pull Request :

• 1.
• . for vertex, distance in shortest_distances.items(): if distance == float('infinity'): print(f'Shortest distance from {start_vertex} to {vertex} is unreachable') else: print(f'Shortest distance from {start_vertex} to {vertex} is {distance}') .