Graphs, BFS and DFS coding problems

Graph problems model grids, networks and dependencies. Practise BFS for shortest paths, DFS for components and cycles, and topological order for prerequisites.

45 problems: 20 easy, 24 medium, 1 hard. Free to read; a free account solves them and earns XP and Aura.

1. Count Black CellsPractice · +10 XP · matrix, traversal, beginnereasy
2. Count Connected NodesPractice · +10 XP · graphs, bfs, dfseasy
3. Count Nodes at Depth KPractice · +10 XP · trees, bfs, dfseasy
4. Count Nodes in ComponentPractice · +10 XP · graphs, bfs, dfseasy
5. Count Tree EdgesPractice · +10 XP · graphs, trees, bfseasy
6. Find Linked List TailPractice · +10 XP · linked structures, arrays, traversaleasy
7. Find Path LengthPractice · +10 XP · linked structures, simulation, traversaleasy
8. Graph Node CountPractice · +10 XP · graphs, bfs, dfseasy
9. Graph Node Degree SumPractice · +10 XP · graphs, bfs, dfseasy
10. Graph Node NeighborsPractice · +10 XP · graphs, adjacency list, bfseasy
11. Graph Path CountPractice · +10 XP · graphs, bfs, pathseasy
12. Matrix Anti-Diagonal SumPractice · +10 XP · matrix, traversaleasy
13. Matrix Diagonal ElementsPractice · +10 XP · matrix, traversaleasy
14. Matrix Element SumPractice · +10 XP · matrix, traversal, loopseasy
15. Matrix Saddle PointsPractice · +10 XP · matrix, grid, traversaleasy
16. Matrix Spiral PrintPractice · +10 XP · matrix, traversaleasy
17. Node Visit OrderPractice · +10 XP · graphs, bfs, dfseasy
18. Print Tree LevelsPractice · +10 XP · trees, traversals, bfseasy
19. Sum of Matrix DiagonalsPractice · +10 XP · matrix, traversaleasy
20. Sum of Subtree SizesPractice · +10 XP · trees, dfs, recursioneasy
21. Array Linked List SimulationPractice · +20 XP · linked structures, simulation, cycle detectionmedium
22. Can Reach All NodesPractice · +20 XP · graphs, bfs, dfsmedium
23. Cycle Detection and RendezvousPractice · +20 XP · linked structures, cycle detection, two pointersmedium
24. Earliest Topological SortPractice · +20 XP · graphs, topological sort, bfsmedium
25. Find Bridges in a TreePractice · +20 XP · graphs, dfs, treesmedium
26. Find Duplicate Cycle EntryPractice · +20 XP · linked structures, hash map, cycle detectionmedium
27. Find First Duplicate Entry PointPractice · +20 XP · linked structures, cycle detection, two pointersmedium
28. Find Longest Path to LeafPractice · +20 XP · trees, dfsmedium
29. Find Minimum Depth Binary TreePractice · +20 XP · recursion, trees, bfsmedium
30. Find the Largest Component SizePractice · +20 XP · graphs, bfs, connected componentsmedium
31. Graph Path ReconstructionPractice · +20 XP · graphs, bfs, shortest pathsmedium
32. Graph Reachability by Edge TypePractice · +20 XP · graphs, bfs, dfsmedium
33. Lexicographically Smallest PathPractice · +20 XP · recursion, dynamic programming, graphsmedium
34. Linked List Jump GamePractice · +20 XP · linked structures, cycle detection, graph traversalmedium
35. Linked List Path SumPractice · +20 XP · linked structures, hash map, cycle detectionmedium
36. Matrix Neighbors SumPractice · +20 XP · matrix, bfs, hash mapmedium
37. Maximum Depth Sum of Unique PathsPractice · +20 XP · trees, bfs, prefix summedium
38. Minimum Path Sum in GridPractice · +20 XP · matrix, dynamic programming, bfsmedium
39. Node Reachability by Path LengthPractice · +20 XP · graphs, bfs, shortest pathsmedium
40. Shortest Path to Target NodePractice · +20 XP · graphs, bfs, shortest pathmedium
41. Tree Diameter and CenterPractice · +20 XP · trees, bfsmedium
42. Tree Path CountPractice · +20 XP · trees, dfsmedium
43. Tree Subtree SumsPractice · +20 XP · trees, dfs, hash mapmedium
44. Unreachable Nodes in a DAGPractice · +20 XP · graphs, topological sort, bfsmedium
45. Minimum Cost Path on a Grid with Custom Edge WeightsPractice · +30 XP · sorting, dijkstra, graphshard