800. Similar RGB Color

800. Similar RGB Color

In the following, every capital letter represents some hexadecimal digit from 0 to f.

The red-green-blue color "#AABBCC" can be written as "#ABC" in shorthand.  For example, "#15c" is shorthand for the color "#1155cc".

Now, say the similarity between two colors "#ABCDEF" and "#UVWXYZ" is -(AB - UV)^2 - (CD - WX)^2 - (EF - YZ)^2.

Given the color "#ABCDEF", return a 7 character color that is most similar to #ABCDEF, and has a shorthand (that is, it can be represented as some "#XYZ"

Example 1:
Input: color = "#09f166"
Output: "#11ee66"
Explanation:  
The similarity is -(0x09 - 0x11)^2 -(0xf1 - 0xee)^2 - (0x66 - 0x66)^2 = -64 -9 -0 = -73.
This is the highest among any shorthand color.

Note:

• color is a string of length 7.
• color is a valid RGB color: for i > 0, color[i] is a hexadecimal digit from 0 to f
• Any answer which has the same (highest) similarity as the best answer will be accepted.
• All inputs and outputs should use lowercase letters, and the output is 7 characters.

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Solution #1

class Solution {
    private static int[] preset = {0,17,34,51,68,85,102,119,136,153,170,187,204,221,238,255};
    private static String[] hex = {"00","11","22","33","44","55","66","77","88","99","aa","bb","cc","dd","ee","ff"};
    public String similarRGB(String color) {
        String s = "#";
        for (int i = 1; i < color.length(); i += 2) {
            int min = 0;
            int cand = toInt(color.charAt(i)) * 16 + toInt(color.charAt(i + 1));
            
            for (int j = 0; j < preset.length; j++) {
                if (Math.abs(cand - preset[j]) < Math.abs(cand - preset[min])) {
                    min = j;
                }
            }
            s += hex[min];
        }
        
        return s;
    }
    
    private int toInt(char c) {
        int rt = 0;
        if (Character.isDigit(c)) {
            rt = c - '0';
        }else {
            rt = 10 + (c - 'a'); 
        }
        
        return rt;
    }
}

Solution #2: https://leetcode.com/problems/similar-rgb-color/discuss/119844/Concise-java-solution