Problems that ask you to build a valid object rather than compute a number. The answer is a construction plus an argument that it works, or a proof that nothing works.
- General — how to attack constructive problems
- Invariants and Monovariants
- Parity and Colouring Arguments
- Extremal Principle
- Small Cases and Pattern Finding
- Classic Constructions — permutations, grids, graphs, sequences
See also: Proof Techniques