source: Codewars
In a factory a printer prints labels for boxes. For one kind of boxes the
printer has to use colors which, for the sake of simplicity, are named with
letters from a to m.
The colors used by the printer are recorded in a control string. For example a
"good" control string would be aaabbbbhaijjjm meaning that the printer used
three times color a, four times color b, one time color h, then one time color
a...
Sometimes there are problems, : lack of colors, technical malfunction and a
"bad" control string is produced e.g. aaaxbbbyyhwawiwjjjwwm with letters not
from a to me.
You have to write a function printer_error which given a string will return
the error rate of the printer as a string representing a rational whose
numerator is the number of errors and the denominator the length of the control
string. Don't reduce this fraction to a simpler expression.
The string has a length greater or equal to one and contains only letters from
a to z.
s = "aaabbbbhaijjjm"
printer_error(s) # => "0/14"
s = "aaaxbbbbyyhwawiwjjjwwm"
printer_error(s) # => "8/22"