Online XorMax
F - Swap and Sort
D - Between Two Binary Strings
G - Divide a Sequence
F - Variety of Digits
G - Range Sort Query
Educational Codeforces Round 45 (Rated for Div. 2) D. Graph And Its Complement
Educational Codeforces Round 46 (Rated for Div. 2) C. Covered Points Count
Codeforces Round #498 (Div. 3) D. Two Strings Swaps
Educational Codeforces Round 47 (Rated for Div. 2) C. Annoying Present