Description

Given an integer, write an algorithm to convert it to hexadecimal. For negative integer, two’s complement method is used.

Example

Input:
26

Output:
"1a"

Input:
-1

Output:
"ffffffff"

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.

Solution

由於二進位制轉十六進位制是四位四位的轉換，所以將compare設為15也就是隻有最低四位為1111其餘都為0，將其與要轉換的數字從低到高四位四位的轉換並新增到字串中。

class Solution
 
 {
	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";
        int compare = 15;	// 2^16-1: 0000...001111
        String res = "";
        while(num != 0) {
        	res = map[(compare & num)] + res;
        	num =
 
 num >>> 4;
        }
        return res;
    }
}