70 lines
2.1 KiB
Rust
70 lines
2.1 KiB
Rust
pub fn letters_to_num(letters: &str) -> Option<u8> {
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let mut num: u8 = 0;
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for (i, letter) in letters.to_ascii_uppercase().chars().rev().enumerate() {
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let n = letter as u8;
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if !(65..=90).contains(&n) {
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return None;
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}
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num = num.checked_add((26_i32.pow(i as u32) * (n as i32 - 64)).try_into().ok()?)?;
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}
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Some(num)
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}
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pub fn num_to_letters(num: u8) -> Option<String> {
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if num == 0 {
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return None;
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} // Otherwise, we will not return none!
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// As another note, we can't represent higher than "IV" anyway;
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// thus there's no reason for a loop (26^n with n>1 will NOT occur).
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let mut text = "".to_string();
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let mut digit1 = num.div_euclid(26u8);
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let mut digit2 = num.rem_euclid(26u8);
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if digit1 > 0 && digit2 == 0u8 {
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digit1 -= 1;
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digit2 = 26;
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}
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if digit1 != 0 {
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text.push((64 + digit1) as char)
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}
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text.push((64 + digit2) as char);
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Some(text.to_string())
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}
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#[cfg(test)]
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mod tests {
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use super::{letters_to_num, num_to_letters};
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#[test]
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fn test_letters_to_num() {
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assert_eq!(letters_to_num("D"), Some(4));
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assert_eq!(letters_to_num("d"), None);
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assert_eq!(letters_to_num("AD"), Some(26 + 4));
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assert_eq!(letters_to_num("CG"), Some(3 * 26 + 7));
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}
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#[test]
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fn test_num_to_letters() {
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println!("27 is {:?}", num_to_letters(27));
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assert_eq!(num_to_letters(1), Some("A".to_string()));
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assert_eq!(num_to_letters(26), Some("Z".to_string()));
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assert_eq!(num_to_letters(27), Some("AA".to_string()));
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assert_eq!(num_to_letters(111), Some("DG".to_string()));
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}
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#[test]
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fn test_l2n_and_n2l() {
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assert_eq!(
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num_to_letters(letters_to_num("A").unwrap()),
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Some("A".to_string())
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);
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assert_eq!(
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num_to_letters(letters_to_num("BJ").unwrap()),
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Some("BJ".to_string())
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);
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for i in 1..=255 {
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assert_eq!(letters_to_num(&num_to_letters(i).unwrap()), Some(i));
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}
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}
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}
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