Algebra and Combinatorics books for Mathematical Olympiads Could you kindly point out to me, some good contest-preparation book's to develop theory and problem solving skills in Algebra? 
It would be good if the book is less of theory and more of problems. I have "Principles and techniques in Combinatorics", but I would like some more difficult books, explaining theory well(this books theory is meh...).
The same for Algebra(polynomials, functional Equations, inequalities, etc.)
Thanks for your help!!!

'Problem Solving Strategies' by Arthur Engel is a classic for math olympiad training at a fairly advanced level. Contains hundreds of problems that take one line to state, two lines to solve with basic means and are still difficult enough to humble olympiad veterans.
