NP-complete problem is a fascinating kind of problem because till now no one has discovered the polynomial-time algorithm to solve it and also no one has proved that no polynomial-time algorithm can exist for any NP-complete problem. It is an open research problem since it was first posed in 1971 to prove P NP. This book specially focused on two NP-complete problems. 1. N-Queens problem: In Year 1848 chess player Max Bezzel had first time propose this problem in the form of 8-queens problem. And more than 100 year researcher try to solve n-queens problem but it's still not completely solved....