- Introduction: Just for Fun!
- String and Algebra (Problem 899)
- Number Theory: Sum of Two Squares Theorem (Problem 633)
- Number Theory: Legendre's Three-Square Theorem (Problem 279)
- Optimization: Optimal Transport I (Problem 1066)
- Combinatorics (Problem 62)
- XOR and Primes (Codeforces 931 D2 XOR Break - Game Version)
- Binary Search on Arbitrary Array (Codeforces 935 E Binary Search)
- Optimization: Optimal Transport II (Problem 979)
- Inversion I: The distribution (Problem 629)
- Optimization: Optimal Transport III (Problem 3189)
- Number Theory: Prime Factorization (Problem 650)