I recently had a Junior Ruby Developer interview where I had to complete a coding challenge live. I didn’t finish in time and didn’t get the position, but I wanted to complete it anyway.

The Challenge:Convert numbers into their word equivalent.

ie. 1 = “one”, 23 = “twenty three”, 1234 = “one thousand two hundred thirty four”

My Solution:

def convert_num(num) ones = { '1' => "one", '2' => "two", '3' => "three", '4' => "four", '5' => "five", '6' => "six", '7' => "seven", '8' => "eight", '9' => "nine" } teens = { '11' => "eleven", '12' => "twelve", '13' => "thirteen", '14' => "fourteen", '15' => "fifteen", '16' => "sixteen", '17' => "seventeen", '18' => "eighteen", '19' => "nineteen" } tens = { '10' => "ten", '20' => "twenty", '30' => "thirty", '40' => "forty", '50' => "fifty", '60' => "sixty", '70' => "seventy", '80' => "eighty", '90' => 'ninety' } hundreds = { '100' => "one hundred", '1000' => "one thousand" } big_num = [] #first check ones place string_num = num.to_s if ones.include?(string_num) ones[string_num] #check teens elsif teens.include?(string_num) teens[string_num] #check tens elsif tens.include?(string_num) tens[string_num] #check hundreds elsif hundreds.include?(string_num) hundreds[string_num] #split the number up else num_array = string_num.split('') if num_array.length == 4 big_num << ones[num_array[0]] + " thousand" big_num << ones[num_array[1]] + " hundred" big_num << tens[num_array[2] + '0'] big_num << ones[num_array[3]] elsif num_array.length == 3 big_num << ones[num_array[0]] + " hundred" big_num << tens[num_array[1] + '0'] big_num << ones[num_array[2]] else big_num << tens[num_array[0] + '0'] big_num << ones[num_array[1]] end big_num.join(" ") end end

How I approached this challenge (my thinking process):

I was told that the highest number passed into this algorithm would be 9,999

- First I knew I needed to create a list of all the numbers and their written equivalent. Since the keys would not match an array index sequence, I decided to store the information in a hash.
- The ones place is its own hash because I knew I would need to use this hash again when dealing with hundreds and thousands.
- I placed the teens in their own hash because there’s no pattern to the written form and would only be used if one if the numbers in the teens hash appeared.
- Same goes for the tens. Twenty is different from two and thirty is different from three. So they get their own hash as well.
- If the number being passed matches exactly with any of the keys in these hashes, then I just need to use that key to grab the value and output it.
- If the number being passed does NOT match with any of the keys in my hashes, then I want to split the number up and search through the array created.
- If the length of the array is 4 (has 4 digits), then I know I need to add the word “thousand” after the first index (0), and “hundred” after the second index (1). I push these in order into a new array called big_num.
- The tens place is tricky as the numbers are all single digits. I add a ‘0’ to the end of the digit and search my tens hash for the matching key.
- I follow this same pattern for numbers that have a length of 3 and numbers with a length of 2.
- Then I join the elements in big_num together so that they form one string.

The following tests and outputs:

p convert_num(3) => "three" p convert_num(15) => "fifteen" p convert_num(90) => "ninety" p convert_num(45) => "forty five" p convert_num(202) => "two hundred two" p convert_num(100) => "one hundred" p convert_num(1200) => "one thousand two hundred" p convert_num(9999) => "nine thousand nine hundred ninety nine"

Pretty sure that there can be some more refactoring, but will have to keep working through the logic to find a way to simplify it.