 Karp's 21 NP-complete problems

Richard Karp’s seminal 1972 paper, "Reducibility Among Combinatorial Problems," identified 21 specific problems that are NP-complete, which means they are among the most challenging problems in computational complexity theory. Below is a list of these 21 problems: 1. **Clique Problem**: Given a graph \( G \) and an integer \( k \), is there a complete subgraph (clique) of size \( k \)?