I have finished theory for single variable calculus taught at high school level, and want a book to practice problem solving in the same. The problem level should be difficult. Also mention some math competitions that include calculus in syllabus (at high school level).
EDIT 01 : The book should not be a tome of thousands of questions, a possible example can be "101 algebra problems by Titu Andresscu". The questions should be math contests style.