Facebook Hacker Cup: Qualification Round

Double Squares

Published Jan 8, 2011 in facebook, hackathon, journal

I had recently registered for Facebook Hacker Cup and decided to take up the challenge. I completed the Double Squares challenge and the Studious Student. As a hacker, an algorithm or a programming hacker, I believe in sharing and definitely LOVE to share.

Well, at the end of the day, I believe everyone has the privilege to learn and the learning process may not be smooth but we all learn eventually.

Somebody once asked, “Explain in human terms or layman terms what is a loop?” Now this is how I will answer:

Learning is a process. I learnt during the process either by my own or through somebody’s help and so on. That’s my learning curve. Now I want to share, so that somebody else will learn and benefit from it. It goes round and never stop. Learning is like a loop.

A double-square number is an integer X which can be expressed as the sum of two perfect squares. For example, 10 is a double-square because 10 = 32 + 12. Your task in this problem is, given X, determine the number of ways in which it can be written as the sum of two squares. For example, 10 can only be written as 32 + 12 (we don’t count 12 + 32 as being different). On the other hand, 25 can be written as 52 + 02 or as 42 + 32.


You should first read an integer N, the number of test cases. The next N lines will contain N values of X.


0 ≤ X ≤ 2147483647
1 ≤ N ≤ 100


For each value of X, you should output the number of ways to write X as the sum of two squares.

Here is how you do it in Ruby.

Source Code (Ruby)

Facebook Hacker Cup: Qualification Round [CLOSED]

End of Qualification Round

Published Jan 11, 2011 in facebook, hackathon, journal