BFS and DFS answer the same question — “which nodes are reachable from a starting node?” — but in different orders and with different properties.
| Property | BFS | DFS |
|---|---|---|
| Data structure | Queue (FIFO) | Stack (LIFO) or recursion |
| Traversal order | Level by level (closest nodes first) | One path fully before backtracking |
| Finds shortest path? | Yes (in unweighted graphs) | No |
| Memory usage | O(width of graph) | O(depth of graph) |
| Cycle detection | Via visited set | Via visited set |
The choice between BFS and DFS is a choice about which order you need results. BFS gives you the nearest results first. DFS gives you complete paths before backtracking.