LeetCode 405 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:

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:26Output:"1a"

Example 2:

Input:-1Output:"ffffffff"

Runtime: 7 ms

static char[] digits = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};public String toHex(int num) {return num >>> 4 == 0 ? String.valueOf(digits[num & 0xf]) : toHex(num >>> 4) + digits[num & 0xf];}

public String toHex2(int num) {String hexs = new String();while (num != 0) {hexs = digits[num & 0xf] + hexs;num = num >>> 4;}return hexs.length() == 0 ? "0" : hexs;}