'''

Given an integer, write an algorithm to convert it to hexadecimal. For negative integer, two’s complement method is used.

Note:

All letters in hexadecimal (a-f) must be in lowercase.
The hexadecimal string must not contain extra leading 0s. If the number is zero, it is represented by a single zero character '0'; otherwise, the first character in the hexadecimal string will not be the zero character.
The given number is guaranteed to fit within the range of a 32-bit signed integer.
You must not use any method provided by the library which converts/formats the number to hex directly.
Example 1:

Input:
26

Output:
"1a"
Example 2:

Input:
-1

Output:
"ffffffff"

'''
import unittest


class Solution(object):
    def toHex(self, num):
        """
        :type num: int
        :rtype: str
        """
        hex_list = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f']
        result = []
        if num == 0:
            return 0
        if num < 0:
            num = 16**8 + num
        while num > 0:
            # print(num)
            num, index = num // 16, num % 16
            # print(num, index)
            result.append(hex_list[index])
        return ''.join(result[::-1])


class TestSolution(unittest.TestCase):

    def test_toHex(self):
        examples = (
            (26, '1a'),
            (0, '0'),
            (-1, 'ffffffff'),
        )
        for first, second in examples:
            self.assert_function(first, second)

    def assert_function(self, first, second):
        self.assertEqual(Solution().toHex(first), second, msg="first: {}; second: {}".format(first, second))


unittest.main()