#8_isUnique.py

# O(N)
import unittest


def unique(string):
    # Assuming character set is ASCII (128 characters)
    if len(string) > 128:
        return False

    char_set = {}
    for char in string:
        if char in char_set:
            # Char already found in string
            return False
        char_set[char] = True

    return True


class Test(unittest.TestCase):
    # unittest provides a base class, TestCase,
    # which may be used to create new test cases.
    dataT = [('abcd'), ('s4fad'), ('')]
    dataF = [('23ds2'), ('hb 627jh=j ()')]

    def test_unique(self):
        # true check
        for test_string in self.dataT:
            actual = unique(test_string)
            self.assertTrue(actual)
        # false check
        for test_string in self.dataF:
            actual = unique(test_string)
            self.assertFalse(actual)


if __name__ == "__main__":
    unittest.main()
    # print(unique('abcd'))