Categorized by difficulty with key concepts. Practice in order: Easy → Medium → Hard.

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#	Problem	Key Concept	Platform
1	Find if Path Exists in Graph	Basic BFS/DFS	LeetCode 1971
2	Flood Fill	DFS on grid	LeetCode 733
3	Number of Islands	DFS/BFS components	LeetCode 200
4	Find Center of Star Graph	Degree counting	LeetCode 1791
5	Find the Town Judge	In/Out degree	LeetCode 997
6	Clone Graph	BFS + HashMap	LeetCode 133

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#	Problem	Key Concept	Platform
1	Course Schedule	Cycle detection (Topo Sort)	LeetCode 207
2	Course Schedule II	Topological Sort (Kahn’s)	LeetCode 210
3	Number of Connected Components	Union-Find / DFS	LeetCode 323
4	Pacific Atlantic Water Flow	Multi-source DFS/BFS	LeetCode 417
5	Rotting Oranges	Multi-source BFS	LeetCode 994
6	Word Ladder	BFS shortest path	LeetCode 127
7	Network Delay Time	Dijkstra	LeetCode 743
8	Is Graph Bipartite?	2-coloring BFS/DFS	LeetCode 785
9	Surrounded Regions	DFS from boundary	LeetCode 130
10	Max Area of Island	DFS component size	LeetCode 695
11	01 Matrix	Multi-source BFS	LeetCode 542
12	Accounts Merge	Union-Find	LeetCode 721
13	Minimum Height Trees	Topological leaf trimming	LeetCode 310
14	Graph Valid Tree	Cycle detection + connectivity	LeetCode 261

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#	Problem	Key Concept	Platform
1	Word Ladder II	BFS + DFS backtrack	LeetCode 126
2	Alien Dictionary	Topological Sort	LeetCode 269
3	Critical Connections in Network	Bridges (Tarjan’s algo)	LeetCode 1192
4	Cheapest Flights Within K Stops	Modified Dijkstra/Bellman-Ford	LeetCode 787
5	Swim in Rising Water	Binary search + BFS or Dijkstra	LeetCode 778
6	Bus Routes	BFS on layered graph	LeetCode 815
7	Shortest Path to Get All Keys	BFS with bitmask state	LeetCode 864
8	Reconstruct Itinerary	Hierholzer’s (Eulerian path)	LeetCode 332
9	Strongly Connected Components	Kosaraju’s / Tarjan’s	Classic CS problem

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Level	Goal	Suggested Problems	Target Time
🟢 Easy	Build fundamentals, understand graph traversal	All 6	2-3 days
🟡 Medium	Master core patterns, apply to grid + graph	First 7	5-7 days
🟡 Medium+	Advanced patterns (Union-Find, Dijkstra)	All 14	7-10 days
🔴 Hard	Multi-algorithm, state-based problems	First 5	Extra practice

💡 Tip: Focus on the Medium problems — they cover 90% of interview graph questions. Hard problems are more common at top-tier companies.

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Before attempting the problems, review Tips & Common Mistakes to avoid pitfalls.

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• Graph Patterns — Review the patterns before solving problems
• Code Examples — Reuse these templates while practicing