Graph
49 problems · 31 with full explanations
2 Easy21 Medium9 Hard
Graph algorithms model relationships between entities. Core algorithms: DFS/BFS for traversal, Dijkstra for weighted shortest path, Bellman-Ford for negative weights, Floyd-Warshall for all-pairs, and Kruskal/Prim for minimum spanning trees. Represent graphs as adjacency lists (Dictionary<int, List<int>>) for efficiency.
How to practice
To practice Graph problems effectively, start with the Easy problems listed below, trace through each solution on paper, then re-implement without looking. When you can recognise the graph pattern within 30 seconds of reading a new problem, move on to Medium difficulty. Use the related topic pages and our study guide for a structured progression.
Start here (Easy + explained)
All Graph problems
- 126.Word Ladder IIHard
- 210.Course Schedule IIMedium
- 310.Minimum Height TreesUnknown
- 684.Redundant ConnectionMedium
- 802.Find Eventual Safe StatesMedium
- 834.Sum of Distances in TreeUnknown
- 851.Loud and RichMedium
- 947.Most Stones Removed with Same Row or ColumnMedium
- 1319.Number of Operations to Make Network ConnectedMedium
- 1334.Find the City With the Smallest Number of Neighbors at a Threshold DistanceMedium
- 1368.Minimum Cost to Make at Least One Valid Path in a GridHard
- 1462.Course Schedule IVMedium
- 1514.Path with Maximum ProbabilityMedium
- 1579.Remove Max Number of Edges to Keep Graph Fully TraversableUnknown
- 1791.Find Center of Star GraphEasy
- 1857.Largest Color Value in a Directed GraphHard
- 1971.Find if Path Exists in GraphEasy
- 1976.Number of Ways to Arrive at DestinationMedium
- 2045.Second Minimum Time to Reach DestinationUnknown
- 2092.Find All People With SecretUnknown
- 2097.Valid Arrangement of PairsUnknown
- 2115.Find All Possible Recipes from Given SuppliesUnknown
- 2127.Maximum Employees to Be Invited to a MeetingUnknown
- 2192.All Ancestors of a Node in a Directed Acyclic GraphMedium
- 2285.Maximum Total Importance of RoadsHard
- 2290.Minimum Obstacle Removal to Reach CornerHard
- 2359.Find Closest Node to Given Two NodesUnknown
- 2392.Build a Matrix With ConditionsHard
- 2440.Create Components With Same ValueMedium
- 2467.Most Profitable Path in a TreeMedium
- 2493.Divide Nodes Into the Maximum Number of GroupsHard
- 2508.Add Edges to Make Degrees of All Nodes EvenHard
- 2509.Cycle Length Queries in a TreeMedium
- 2577.Minimum Time to Visit a Cell In a GridHard
- 2685.Count the Number of Complete ComponentsMedium
- 2699.Modify Graph Edge WeightsUnknown
- 2924.Find Champion IIMedium
- 2976.Minimum Cost to Convert String IMedium
- 2977.Minimum Cost to Convert String IIUnknown
- 3108.Minimum Cost Walk in Weighted GraphUnknown
- 3203.Find Minimum Diameter After Merging Two TreesMedium
- 3243.Shortest Distance After Road Addition Queries IUnknown
- 3310.Remove Methods From ProjectUnknown
- 3341.Find Minimum Time to Reach Last Room IMedium
- 3342.Find Minimum Time to Reach Last Room IIMedium
- 3372.Maximize the Number of Target Nodes After Connecting Trees IMedium
- 3373.Maximize the Number of Target Nodes After Connecting Trees IIUnknown
- 3600.Maximize Spanning Tree Stability with UpgradesUnknown
- 3651.Minimum Cost Path with TeleportationsUnknown