NP-Completeness
An NP-complete problem belongs to NP and has every NP problem polynomially reducible to it; these are the hardest problems in NP.
Purpose
To understand the complexity hierarchy and recognize intractable problems.
Mechanism
NP: verifiable in polynomial time. NP-hard: every NP problem reduces to it. NPC=NP∩NP-hard. If any NPC problem has a polynomial solution, then P=NP. Classics: SAT, TSP, vertex cover.
Use cases
- Complexity analysis
- Problem hardness assessment
- Reduction proofs