LeetCode_405. Convert a Number to Hexadecimal

Posted 2020-11-22 邓戈麟

 

405. Convert a Number to Hexadecimal

Easy

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

Note:

1. All letters in hexadecimal (a-f) must be in lowercase.
2. 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.
3. The given number is guaranteed to fit within the range of a 32-bit signed integer.
4. 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"

 

package leetcode.easy;

public class ConvertANumberToHexadecimal {
	char[] map = { ‘0‘, ‘1‘, ‘2‘, ‘3‘, ‘4‘, ‘5‘, ‘6‘, ‘7‘, ‘8‘, ‘9‘, ‘a‘, ‘b‘, ‘c‘, ‘d‘, ‘e‘, ‘f‘ };

	@org.junit.Test
	public void test() {
		System.out.println(toHex(26));
		System.out.println(toHex(-1));
	}

	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;
	}
}