Similar rgb color

Math String Enumeration

67.9% acceptance

Mar 31, 2026

112

692

The red-green-blue color "#AABBCC" can be written as "#ABC" in shorthand. For example, "#15c" is shorthand for the color "#1155cc". The similarity between the two colors "#ABCDEF" and "#UVWXYZ" is -(AB - UV)2 - (CD - WX)2 - (EF - YZ)2. Given a string color that follows the format "#ABCDEF", return a string represents the color that is most similar to the given color and has a shorthand (i.e., it can be represented as some "#XYZ"). Any answer which has the same highest similarity as the best answer will be accepted.

Solution

Rust

Time O(2^n)

Space O(n)

LeetCode

solution.rs

impl Solution {
  pub fn similar_rgb(color: String) -> String {
    let bytes = color.as_bytes();
    let mut result = String::from("#");
    for i in 0..3 {
      let hi = Self::hex_val(bytes[1 + i * 2]);
      let lo = Self::hex_val(bytes[2 + i * 2]);
      let val = (hi << 4) | lo;
      let best = ((val as f64 / 17.0).round() as u32).min(15) * 17;
      result.push(char::from_digit(best / 16, 16).unwrap());
      result.push(char::from_digit(best % 16, 16).unwrap());
    }
    result
  }

  fn hex_val(b: u8) -> u32 {
    if b.is_ascii_digit() { (b - b'0') as u32 } else { (b - b'a' + 10) as u32 }
  }
}