Write a function
titleToNumber(title) or title_to_number(title) or titleToNb title ...
(depending on the language)
that given a column title as it appears in an Excel sheet, returns its corresponding column number. All column titles will be uppercase.
Examples:
titleTonumber('A') === 1
titleTonumber('Z') === 26
titleTonumber('AA') === 27
Note for Clojure:
Don't use Java Math/pow (even with bigint) because there is a loss of precision
when the length of "title" is growing.
Write your own function "exp [x n]".