An internet search for the terms "algorithms and complexity" delivers a myriad of links, topped by the popular website for this book.
Updated and back in print, this classic text provides the perfect introduction to the tools of algorithmic design and analysis, concentrating on basic principles and illustrating them with well-chosen paradigms such as:
• Fast Fourier Transform
• NP-Completeness
• Number Theory and Cryptography
Including updated topics for the new edition:
• The Network Flow Algorithm
• A breakthrough result in Primality Testing
And very importantly, it contains solutions and hints for most of the problems.