Which of the following algorithm can be used to efficiently calculate ...
Understanding Shortest Path Algorithms in DAGs
In a Directed Acyclic Graph (DAG), the single-source shortest path problem can be efficiently solved by leveraging the properties of the graph. Among the options provided, the correct choice is:
Topological Sort
Why Topological Sort?
- DAG Properties: A DAG is a directed graph with no cycles. This allows for a linear ordering of its vertices, known as topological ordering.
- Process of Topological Sort:
- Perform a topological sort on the DAG to obtain a linear ordering of vertices.
- This ordering ensures that for any directed edge (u, v), vertex u comes before vertex v.
- Relaxation of Edges:
- Start from the source vertex and initialize its distance to zero, while all other vertices are set to infinity.
- Traverse the vertices in topological order and relax all outgoing edges of the current vertex. This means updating the distance of each adjacent vertex if a shorter path is found.
Efficiency
- Time Complexity: The topological sort can be performed in O(V + E) time, where V is the number of vertices and E is the number of edges. The relaxation step also takes O(V + E) time.
- Overall: The combined complexity remains O(V + E), making it efficient for single-source shortest path calculations in DAGs.
Comparison with Other Algorithms
- Dijkstra's Algorithm: Best for graphs with non-negative weights, but not optimal for DAGs.
- Bellman-Ford Algorithm: Handles negative weights, but is less efficient (O(VE)).
- Strongly Connected Components: Not applicable for finding shortest paths directly.
In summary, using topological sorting in a DAG provides a clear and efficient method to solve the single-source shortest path problem.
Which of the following algorithm can be used to efficiently calculate ...
Using Topological Sort, we can find single source shortest paths in O(V+E) time which is the most efficient algorithm. See following for details. Shortest Path in Directed Acyclic Graph