I was looking for a good way to convert a number to the Excel column letter, for example:

1 -> A

26 -> Z

27 -> AA

28 -> AB

800 -> ADT

etc.

After searching on Google, I could not find any algorithm I want. (The closest one can handle up to two letters, i.e., ZZ. It will crash if the number is too large.). So I ended up creating my own.

Basically, you can think of this problem as a 26 based number conversion. Here is the php version. It should be pretty simple to convert it to a different language. Let me know if you have any problem.

function columnLetter($c){ $c = intval($c); if ($c < = 0) return ''; $letter = ''; while($c != 0){ $p = ($c - 1) % 26; $c = intval(($c - $p) / 26); $letter = chr(65 + $p) . $letter; } return $letter; }

Usage: columnLetter(1303618093); //DERRICK

Note that if you prefer lower cases rather than upper cases, you can simply replace 65 by 96 in the code.

Enjoy~!

–Derrick

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