40. DFS vs. BFS: Choosing the Right Traversal
Both DFS and BFS have the same asymptotic time complexity, O(V + E) when using an Adjacency List, but they solve different problems best.
| Feature | DFS (Depth First Search) | BFS (Breadth First Search) |
|---|---|---|
| Data Structure | Stack (or Recursion) | Queue |
| Search Pattern | Deep, exhausting one path first | Wide, exploring layer by layer |
| Time Complexity | O(V + E) | O(V + E) |
| Space Complexity | O(H) where H is graph height | O(B) where B is max width/number of nodes at one level |
| Best For | Cycle detection, topological sort, exploring large, deep structures (if the target is likely deep). | Finding shortest paths (unweighted), finding connected components, shallow exploration (if the target is likely close to the start). |