lc405. Convert a Number to Hexadecimal

405. Convert a Number to Hexadecimal Easy

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Share 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"

思路：位運算,16進制，把num與0b1111與運算，獲取字典表下標（‘0123456789abcdef’），組合

代碼:python3

class Solution:
    def toHex(self, num: int) -> str:
        if num==0:return '0'
        np='0123456789abcdef'
        result=''
        while num:
        	s=num&0xf
        	result = np[s]+result
        	num = num>>4 if num>0 else(num%0x100000000)>>4
        return result
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