Binary Swaps
Codeforces Round 301 (Div. 2) B. School Marks
Codeforces Round 304 (Div. 2) D. Soldier and Number Game
Codeforces Round 313 (Div. 1) B. Equivalent Strings
Codeforces Round #Pi (Div. 2) C. Geometric Progression
Codeforces Round #Pi (Div. 2) D. One-Dimensional Battle Ships
Alice’s Tree
All Numbers
Flipping Matrix
Find Path Union