exercise.py

def obter_mais_longa_substring(s):
    alfabeto = {'a':1,'b':2,'c':3,'d':4,'e':5,'f':6,'g':7,'h':8,'i':9,'j':10,'k':11,'l':12,'m':13,'n':14,'o':15,'p':16,'q':17,'r':18,'s':19,'t':20,'u':21,'v':22,'w':23,'x':24,'y':25,'z':26}

    substrings = []
    substring_atual = []
    posicao_anterior = 0
    for c in s:

        posicao_atual = alfabeto[c]

        if posicao_atual >= posicao_anterior:
            substring_atual.append(c)
            posicao_anterior = posicao_atual
        else:
            substrings.append(substring_atual)
            substring_atual = []
            substring_atual.append(c)
            posicao_anterior = 0

    substrings.append(substring_atual)

    maior_substring = []
    tam_maior_substring = 0

    for substring in substrings:
        if len(substring) > tam_maior_substring:
            maior_substring = substring
            tam_maior_substring = len(substring)

    return ''.join(maior_substring)

# Alguns testes
print(obter_mais_longa_substring('azcbobobegghakl')) # beggh
print(obter_mais_longa_substring('aabbbabcdefgh')) # abcdefgh
print(obter_mais_longa_substring('zzabcxxxxxxx')) # abcxxxxxxx
print(obter_mais_longa_substring('aaaaaaaaaaaa')) # aaaaaaaaaaaa
print(obter_mais_longa_substring('nehl')) # ehl
print(obter_mais_longa_substring('python')) # tho

https://gist.github.com/aantunes123/22df84dc8092b05ac0f8e78221d346dc