find a length the longest substring that consists of the same char. The discussion The mission

checkio('sdsffffse') == 4
checkio('ddvvrwwwrggg') == 3

find the longest substring without repeating chars. The discussion The mission

checkio('aaaaa') == 'a'
checkio('abdjwawk') == 'abdjw'

find a length the longest substring that repeats more than once. The discussion The mission

checkio('aaaa') == 2
checkio('abc') == 0
checkio('aghtfghkofgh') == 3 # fgh

find first the longest repeating substring The discussion The mission

checkio('aaaaa') == 'aaaaa'
checkio('aabbff') == 'aa'
checkio('aababcc') == 'abab'
checkio('abcabcabab') == 'abcabc'