pub fn longest_common_prefix(strings: Vec<String>) -> String {
  // Sort the strings ascending by length.
  let mut strings = strings.clone();
  strings.sort_by(|a, b| a.len().cmp(&b.len()));

  // Then grab the shortest string.
  let shortest_string = match strings.first() {
    Some(string) => string,
    None => return String::new(),
  };

  // The shortest string must be the maximum possible prefix, so start with it.
  let mut prefix = shortest_string.clone();

  // Then loop over the shortest string's length and check if every string in
  // the list starts with the prefix, and if they don't, pop the last character
  // from the prefix.
  for _ in 0..shortest_string.len() {
    // If we find a prefix that all strings start with, we've found the longest
    // common one.
    if strings.iter().all(|string| string.starts_with(&prefix)) {
      break;
    } else {
      prefix.pop();
    }
  }

  // If by the end there is no longest common prefix, the prefix will be an
  // empty string.
  prefix
}

#[test]
fn test_longest_common_prefix() {
  assert_eq!(
    longest_common_prefix(vec![
      "doggo".to_string(),
      "doggie".to_string(),
      "dog".to_string(),
    ]),
    "dog"
  );

  assert_eq!(
    longest_common_prefix(vec![
      "flower".to_string(),
      "flow".to_string(),
      "flight".to_string(),
    ]),
    "fl"
  );

  assert_eq!(
    longest_common_prefix(vec![
      "dog".to_string(),
      "racecar".to_string(),
      "car".to_string(),
    ]),
    ""
  );

  assert_eq!(
    longest_common_prefix(vec![
      "dog".to_string(),
      "racecar".to_string(),
      "car".to_string(),
      "".to_string()
    ]),
    ""
  );
}