Leetcocde 405.Convert a Number to Hexadecimal

Description

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"

Solution

给我们一个数字num,让将它转成16进制的数。

这里最简单的方法就是每次取num后四位二进制,然后再将num逻辑右移四位。

class Solution {
    String hex = "0123456789abcdef";

    public String toHex(int num) {
        if (num == 0) return "0";
        String res = "";
        while (num != 0) {
            res = hex.charAt(num & 15) + res;
            num = num >>> 4;
        }
        return res;
    }
}

同理,以后无论是转成多少进制,都可以用这种方法。

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