Leetcode 405. Convert a Number to Hexadecimal 16进制转化 解题报告

1 解题思想

2 原题

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"

3 AC解

public class Solution {
//直接将num当做二进制的数字去处理，然后每4位映射一次就好,然后逻辑位移就好
char[] map = {'0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f'};
public String toHex(int num) {
if(num == 0) return "0";
StringBuilder sb = new StringBuilder();
while(num != 0){
sb.append(map[(num & 15)]);
num = (num >>> 4);
}
sb.reverse();
return sb.toString();
}
}