longest substring without repeating characters

lols.py

# longest substring without repeating characters

class lols:
    def __init__(self, string : str):
        self.string = string
    def solve(self) -> int:
        if len(self.string) == 0:
            return 0
        if len({self.string[i] : i for i in range(len(self.string))}) == 1:
            return 1
        sub_s = []
        ls = self.string[0]
        last_char = self.string[0]
        for c in range(1, len(self.string)):
            if self.string[c] != last_char:
                ls+=self.string[c]
            elif self.string[c] == last_char:
                ls = self.string[c]
            if len(ls) > 1:
                sub_s.append(ls)
            last_char = self.string[c]
        last_sub = sub_s[len(sub_s)-1]
        dict_sub_s = {last_sub[i] : i for i in range(len(last_sub))}
        return len(dict_sub_s)

                            
user_input = input("Enter String >>> ")
assert 0 <= len(user_input) <= 5 * 104
p = lols(user_input)
n_sub_str = p.solve()
print(n_sub_str)