Leetcode: Convert a Number to Hexadecimal

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"

记住要delete begining 0

public class Solution {
    public String toHex(int num) {
        StringBuffer res = new StringBuffer();
        String[] charMap = new String[]{"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f"};
        for (int i=0; i<8; i++) {
            int number = num & (0b1111);
            num = num >>> 4;
            res.insert(0, charMap[number]);
        }
        while (res.charAt(0)=='0' && res.length()>1) res.deleteCharAt(0);
        return res.toString();
    }
}

 

要记住单独处理 num == 0的情况

public class Solution {
    public String toHex(int num) {
        if (num == 0) return "0";
        StringBuffer res = new StringBuffer();
        String[] charMap = new String[]{"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f"};
        while (num != 0) {
            int number = num & (0b1111);
            num = num >>> 4;
            res.insert(0, charMap[number]);
        }
        return res.toString();
    }
}