题目
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"
难度
Easy
方法
对于num，每次num&15便可取到最右的4个bit位，然后num>>4循环处理即可将num转换为16进制。因为num范围为32bit位，因此最多右移8次，每次右移4个bit位。当num不为0时，转换为16进制后，前面有0需去除。
python代码
class Solution(object):
def toHex(self, num):
"""
:type num: int
:rtype: str
"""
if num == 0:
return "0"
map = ["0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f"]
hex = ""
for i in range(8):
hex = map[num & 0xf] + hex
num = num >> 4
return hex.lstrip("0")
assert Solution().toHex(-1) == "ffffffff"
assert Solution().toHex(26) == "1a"
