Graph Basics: Adjacency Lists, BFS and DFS Traversal
Sparse graphs are kept as adjacency lists and BFS finds the fewest steps in O(V + E); on a 5,000-vertex graph BFS over an adjacency matrix is 46 times slower. We write a generic Graph, BFS distances and paths, recursive and iterative DFS, connected components and a grid flood fill in C#, and show with real output that marking visited on dequeue makes 2 million enqueues instead of 2,000.
8 Nov 2026
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12 min
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2
