Special graphs
Subsequences
Equal bitwise operations
Codeforces Round 699 (Div. 2) D. AB Graph
Educational Codeforces Round 104 (Rated for Div. 2) E. Cheap Dinner
Codeforces Round 705 (Div. 2) C. K-beautiful Strings
Codeforces Round 710 (Div. 3) F. Triangular Paths
Codeforces Round 710 (Div. 3) G. Maximize the Remaining String
Path with hyperloops
Shortest Path Revisited