happy_number.rb

# https://leetcode.com/problems/happy-number/
#
# Write an algorithm to determine if a number is "happy". A happy number is a
# number defined by the following process: Starting with any positive integer,
# replace the number by the sum of the squares of its digits, and repeat the
# process until the number equals 1 (where it will stay), or it loops
# endlessly in a cycle which does not include 1. Those numbers for which this
# process ends in 1 are happy numbers.
#
# Example:
#
#     19 is a happy number:
#
#         1^2 + 9^2 = 82
#         8^2 + 2^2 = 68
#         6^2 + 8^2 = 100
#         1^2 + 0^2 + 0^2 = 1
#
# Credits:
#
#     Special thanks to @mithmatt and @ts for adding this problem and creating
#     all test cases.


# @param {Integer} n
# @return {Boolean}
def is_happy(n)
  map = {}
  while true
    s = 0
    while n > 0
      s = s + (n % 10) * (n % 10)
      n = n / 10
    end
    return true if s == 1
    return false if map[s]

    map[s] = true
    n = s
  end
end