How to get Excel column title? [duplicate]

Question

I try to resolve some task in code wars. I have to create method, which returns column title(occurring in Excel). The method gets one parameter, it's number. For example:

def get_column_title(n)
//code
end

If n = 1. It should return A.

Test cases:

Test.assert_equals(get_column_title(1), "A")
Test.assert_equals(get_column_title(26), "Z")
Test.assert_equals(get_column_title(52), "AZ")
Test.assert_equals(get_column_title(53), "BA")
Test.assert_equals(get_column_title(702), "ZZ")

What I have:

  def number_values
    {
      1 => 'A', 2 => 'B', 3 => 'C', 4 => 'D', 5 => 'E', 6 => 'F', 7 => 'G',
      8 => 'H', 9 => 'I', 10 => 'J', 11 => 'K', 12 => 'L', 13 => 'M', 14 => 'N',
      15 => 'O', 16 => 'P', 17 => 'Q', 18 => 'R', 19 => 'S', 20 => 'T',
      21 => 'U', 22 => 'V', 23 => 'W', 24 => 'X', 25 => 'Y', 26 => 'Z'
    }
  end

def translate_values
    if @n <= 26
      number_values[@n-26*0]
    elsif @n <= 52
        'A'+ number_values[@n-26*1]
    elsif @n <= 78
        'B' + number_values[@n-26*2]
    end
end

Issue: I don't know how to resolve this task algorithmically. I thought about dividing the number by 26 in a loop. Can you give me some hints how to approach the task?

Source of exercise: codewars.com

have a look at stackoverflow.com/a/182924/390819

Cristian Lupascu
– Cristian Lupascu

2016-09-15 14:03:39 +00:00
Commented Sep 15, 2016 at 14:03 — Cristian Lupascu
– Cristian Lupascu, Commented Sep 15, 2016 at 14:03

Saeid · Accepted Answer · 2016-09-15 14:34:50Z

1

You have to convert your number to Base 26 and use A...Z instead of 0...25. The only trick is to subtract one from your number in each step.

edited Sep 15, 2016 at 14:34

answered Sep 15, 2016 at 14:00

Saeid

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Saeid · Accepted Answer · 2016-09-15 15:42:56Z

1

{alphabetCount=26
alphabetOffset=1

for i in 0 .. 1000
    i = i + alphabetOffset
    category=""

    while i>alphabetCount do
        j=i%alphabetCount

        if j==0 then
            j=alphabetCount
        end

        category=(64+j).chr + category
        i=(i-j)/alphabetCount

        if j==0 then
            i=i-1
         end
    end

    category=(64+i).chr + category + "\n"
    puts category
end}

sorry if it is a bit wonky but i am in mobile and could only test via an online compiler :( but it outputs

0=A
...
25=Z
....
702=AAA

edited Sep 15, 2016 at 15:42

Saeid

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answered Sep 15, 2016 at 15:40

alex

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