Problem

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.

Solution: Brute Force

R, G, B are independent, find the closest color for each channel separately.

Time complexity: O(3 * 16)

Space complexity: O(1)

// Author: Huahua

// Running time: 7 ms

class Solution {

public:

string similarRGB(string color) {

const string hex{"0123456789abcdef"};

vector<int> rgb(3, 0);

for (int i = 0; i < 3; ++i)

rgb[i] = hex.find(color[2 * i + 1]) * 16 + hex.find(color[2 * i + 2]);

string ans(7, '#');

for (int i = 0; i < 3; ++i) {

int best = INT_MAX;

for (int j = 0; j < 16; ++j) {

int diff = abs(j * 16 + j - rgb[i]);

if (diff >= best) continue;

best = diff;

ans[2 * i + 1] = ans[2 * i + 2] = hex[j];

}

return ans;

}

};

Posts tagged as “rgb”

花花酱 LeetCode 800. Simple RGB Color

Problem

Note:

Solution: Brute Force