leetcode405.Convert a Number to

原题链接：https://leetcode.com/problems/convert-a-number-to-hexadecimal/

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"

class Solution:
    def toHex(self, num: int) -> str:
        if not isinstance(num, int):
            return False
        num_to_letter = "0123456789abcdef"
        res = ""
        count = 0
        if num < 0:
            num += 2 ** 32
        while num > 0 and count < 8:
            res =  num_to_letter[num & 15] + res
            count += 1
            num >>= 4
        return res if res else "0"