Shor the Duck's SG Collection, a curated problemset split into difficulties of the best problems on Codebreaker set by the SG IO Community!
Criteria for 5 star:
Thinking requirement may be significantly higher than 4 star.
Expansions on previous techniques like DP or Dijkstra such as constructing your own graph may be included.
Basics of Segment Tree, DSU, and MST may also be included.
Should be challenging for Codeforces Specialists, and suitable for Codeforces Experts