Problems
The Bottom of a Graph#6223
Very easy · Graphs
Dark Roads#6224
Easy · Greedy algorithms · Disjoint set union · Sorting
Beacons#6225
Very hard · Graphs
Food Review#6226
Very hard · Graphs · Shortest paths
From Dusk Till Down#6227
Easy · Graphs · Shortest paths
Fenwick Tree#6233
Very easy · Prefix Sums · Data Structures · Implementation
Honey Bees#6239
Very easy · Implementation
Repeating Decimals#6240
Easy · Implementation
Solutions of Cubic Equation#6241
Hard · Math · Implementation
Multiplication in a Dihedral Group#6242
Easy · Implementation · String suffix structures
Area Between Outer Hull and Inner Hull#6243
Medium · Geometry
Sharkovski's Ordering#6244
Very easy · Implementation
Metro Manila Detour#6245
Very easy · Graphs
More Fun in Bicol#6246
Very hard · Implementation
Interior Lattice Points#6247
Very easy · Geometry
Permutations#6248
Very easy · Math · Brute force
Planting Trees#6249
Very easy · Sorting · Greedy algorithms
Boiling Vegetables#6250
Very easy · Greedy algorithms
Number Trick#6251
Easy · Brute force
Robert Hood#6252
Hard · Geometry · Convex Hull
Virus Replication#6253
Very easy · Implementation
Timebomb#6254
Very easy · Implementation
Erase Securely#6255
Very easy · Math
Pinball#6256
Very hard · Geometry
Dance Reconstruction#6257
Hard · Math · Combinatorics · Number theory · Constructive Algorithms