View All num of num See all Photos Google www.google.com Engaged Employer Overview Reviews Salaries Interviews Jobs Photos Benefits 3.2k Reviews 11k Salaries 3.9k Interviews Follow Add Review or Salary Follow Add Review or Salary Interview Question Software Engineer Interview Google What is the total number of different valid parenthesis. I mean not to code it out, but to calculate the number. Tags: See more , See less 8 Answer Add Tags Answer Interview Answer 1 Answer ▲ 1 ▼ it is the Catalan number = (2n -2) ! /( n! (n-1)!) Vivek on Nov 11, 2013 Interviews > Software Engineer > Google Add Answers or Comments To comment on this, Sign In or Sign Up.