The Art of Problem Solving Vol 1: The Basics

美国数学天赋班培训教材，英文原版。作者：Sandor Lehoczky， Richard Rusczyk。
This book is about methods. If you find yourself memorizing formulas, you are missing the
point. The formulas should become obvious to you as you read, without need of memorization.
This is another function of the examples and exercises: to make the methods part of the way you think, not just some process you can remember.