Persistence.rb

# Description:

# Write a function, persistence, that takes in a positive parameter num and returns its multiplicative persistence, which is the number of times you must multiply the digits in num until you reach a single digit.

# For example:

#  persistence(39) # returns 3, because 3*9=27, 2*7=14, 1*4=4
#                  # and 4 has only one digit

#  persistence(999) # returns 4, because 9*9*9=729, 7*2*9=126,
#                   # 1*2*6=12, and finally 1*2=2

#  persistence(4) # returns 0, because 4 is already a one-digit number


# Test

puts persistence(39)
puts "Should return 3"

puts persistence(4)
puts "Should return 0"

puts persistence(25)
puts "Should return 2"

puts persistence(999)
puts "Should return 4"



# My Solution
def persistence(n)
  ctr = 0
   while (n > 9)
     n = n.to_s.chars.map(&:to_i).reduce(:*)
      ctr+=1
   end  
   ctr
end