405. Convert a Number to Hexadecimal

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/*
405. Convert a Number to Hexadecimal   
Total Accepted: 5643
Total Submissions: 13518
Difficulty: Easy
Contributors: Admin
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"
Hide Tags Bit Manipulation
*/

	/*
	Basic idea: each time we take a look at the last four digits of
	            binary verion of the input, and maps that to a hex char
	            shift the input to the right by 4 bits, do it again
	            until input becomes 0.
		https://discuss.leetcode.com/topic/60365/simple-java-solution-with-comment/2
	*/
	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";
		String result = "";
		while(num != 0) {
			result = map[(num & 15)] + result;
			num = (num >>> 4);
		}
		return result;
	}