The tune with no repeated notes

Problem

"Give me a passage where no note sounds twice," the choir director asks Julian. He has the whole piece written on a single line, and he is after the longest unbroken stretch that fits.

Write a function that takes notes, a string where each character is a note, an uppercase letter from A to G (it may be empty), and returns a whole number: the length of the longest unbroken stretch in which no character repeats. Unbroken means no notes are skipped.

With "ABCAD" it returns 4: "ABC" cannot grow, because the A is already in it, but "BCAD" fits whole.

The repeat can be far away: in "CDC" the longest stretch is 2, not 3.

A single note is already a stretch of length 1, and an empty string is 0.

Examples

• The example

  "ABCAD" → 4

• Nothing repeats

  "CDEFG" → 5

• The repeat is not next to it

  "CDC" → 2

• The same note four times

  "EEEE" → 1

Besides these, the challenge has hidden tests that are revealed when you submit your solution.

You start with this

def fresh_stretch(notes):
    pass

function freshStretch(notes) {
}