Graphs

Patterns to know:

• BFS/DFS traversal.
• Union-Find (connected components, cycle detection).
• Topological Sort (Kahn’s algorithm or DFS).
• Dijkstra / Bellman-Ford / A*.

How to identify:

• Input: nodes + edges or 2D grid.
• “Number of islands / connected components” → DFS/BFS.
• “Prerequisites / ordering” → topological sort.
• Weighted shortest path → Dijkstra.