Breadth-first Search
Problems on breadth-first search, including shortest paths in unweighted graphs, mazes and grids, knight and other chess-piece moves, flood fill, puzzles where each state is a vertex, and searches that start from several sources at once.
The Graphs section of the library covers breadth-first search, multi-source BFS, 0-1 BFS and graphs of states. Related problem sets are under Shortest paths and Depth-first search.
Problems
Fence#6579
Medium
Worst Case Scenario#6610
Medium
Eating Brains#6696
Very hard
Grasshopper#6917
Medium
The Leprechaun Hunt#7732
Very hard
Catch That Cow#7748
Medium
Button Bashing#8338
Medium
Colorgraph#8561
Hard
Bitmap#10049
Medium
Snow Boots#10409
Medium
Push a Box#10519
Hard
Emails#10730
Hard
Daisy's Mazes#10731
Very hard
Fantasmagorie#10734
Very hard