Bitsets
Problems on bitsets, including speeding up dynamic programming over subset sums, reachability and transitive closure in dense graphs, counting triangles and common neighbours, and comparing many binary rows at once.
The bitmasks article in the Basics section covers the bit operations a bitset is built on. Related problem sets are under Bitwise operations and Bitmasks.
Problems
LCA#3298
Medium
False figures#4598
Very hard
Cinema tickets#5463
Medium
Board Blitz#7316
Hard
Pixels#9706
Hard
Quests#11573
Very hard
The Root of Evil#11697
Very hard
Simple Problem#12288
Very hard