"Introduction to Algorithms" by Thomas H. Cormen, Charles E. Leiserson, Ronald L. Rivest, Clifford Stein.

"Algorithm Design" by Jon Kleinberg, Éva Tardos.

"Introduction to the Theory of Computation" by Michael Sipser.

"Course notes for CSC B36/236/240: Introduction to the Theory of Computation" by Vassos Hadzilacos. http://www.cs.toronto.edu/~vassos/b36-notes/notes.pdf