[Leetcode] 405. Convert a Number to Hexadecimal 解题报告
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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
0
s. 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:26Output:"1a"
Example 2:
Input:-1Output:"ffffffff"
思路:
由于16是2的次幂,并且整数在计算机中都是以二进制的形式表示的,所以转化为16进制的方法非常简单:每次获得二进制的最低4位,直接将其转换为16进制的表示即可。在C++中实现需要注意的一点是:由于有符号整数和无符号整数在负数情况下的循环移位有所不同,所以我们在对num进行循环移位前,需要首先将其显式转换为无符号整数,这样可以统一处理正整数和负整数。
这道题目虽然也可以用传统的除余法解决,但是代码就相对复杂多了,而且处理补码的情况比较麻烦。
代码:
class Solution {public: string toHex(int num) { string ret(""); string hex_chars("0123456789abcdef"); while (num) { ret.push_back(hex_chars[num & 0xF]); num = (unsigned)num >> 4; } reverse(ret.begin(), ret.end()); return ret.empty() ? "0" : ret; }};
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