What is the time complexity of a depth-first search (DFS) on a graph?

Practice Questions

Q1
What is the time complexity of a depth-first search (DFS) on a graph?
  1. O(V)
  2. O(E)
  3. O(V + E)
  4. O(V * E)

Questions & Step-by-Step Solutions

What is the time complexity of a depth-first search (DFS) on a graph?
  • Step 1: Understand that a graph consists of vertices (nodes) and edges (connections between nodes).
  • Step 2: Recognize that during a depth-first search (DFS), we explore each vertex in the graph.
  • Step 3: Note that for each vertex we visit, we also look at all the edges connected to that vertex.
  • Step 4: Realize that in the worst case, we will visit every vertex (V) and every edge (E) in the graph.
  • Step 5: Combine the visits to vertices and edges to express the total work done: O(V) for vertices and O(E) for edges.
  • Step 6: Conclude that the overall time complexity of DFS is O(V + E).
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