Program calculus problem.

Fibonacci with a twist.

Combinorics about permutations and inversions.

Combinatorics problem on multisets.

Little number theory puzzle.

Crossing a bridge while satisfying constraints.

Dutch National Flag Problem.

FFT uses.

Reasoning with loop invariants.

Cool proof of the Schröder-Bernstein Theorem.

Program calculus problem.

Line of airline passengers boarding a plane.

Induction and integer inequalities.

Inclusion-exclusion in combinatorics.

Network flows and vertex covers.

Hamming codes solve an impossible looking puzzle.

Little nugget.

Coin weighings problems.

Variants of the Bernoulli inequality.

Completeness of the Reals.