convert-a-number-to-hexadecimal.py

# -*- coding:utf-8 -*-


#
# 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(object):
    def toHex(self, num):
        """
        :type num: int
        :rtype: str
        """
        lstHex = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f']
        if num == 0:
            return '0'
        if num == -1:
            return 'ffffffff'
        if num < 0:
            num = num + 2**32
        stack = []
        while num>=16:
            t = num%16
            stack.append(lstHex[t])
            num = num/16
        stack.append(lstHex[num])
        stack.reverse()
        return ''.join(stack)