405. Convert a Number to Hexadecimal 数字转换为十六进制数

@TOC

# 题目描述

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"
``````

# 解题方法

# Java解法

``````public class Solution {
public String toHex(int num) {
char[] hexs = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
if (num == 0) {
return "0";
}
while (num != 0) {
answer.insert(0, hexs[(16 + num % 16) % 16]);
num = num >>> 4;
}

}
}
``````

AC: 8 ms

# Python解法

``````class Solution(object):
def toHex(self, num):
"""
:type num: int
:rtype: str
"""
if num == 0:
return "0"
res = ""
if num < 0:
num += 1 << 32
while num != 0:
last = num % 16
if last < 10:
res = str(last) + res
else:
res = chr(last - 10 + ord('a')) + res
num /= 16
return res
``````

# 日期

2017 年 1 月 14 日 2018 年 11 月 20 日 —— 真是一个好天气