Refactor Pangram Implementation (TheAlgorithms#795)

* ref: improve implementation - Rewrite docstring - Rewrite tests using macro * feat(tests): add some edge tests * style: simplify `alphabet` * style: use the name `used_letters` * refactor: add `compute_letter_counts` --------- Co-authored-by: vil02 <65706193+vil02@users.noreply.github.com>

Author: sozelfist

src/string/pangram.rs

@@ -1,54 +1,53 @@
+//! This module provides functionality to check if a given string is a pangram.
+//!
+//! A pangram is a sentence that contains every letter of the alphabet at least once.
+//! This module can distinguish between a non-pangram, a regular pangram, and a
+//! perfect pangram, where each letter appears exactly once.
+
 use std::collections::HashSet;
 
+/// Represents the status of a string in relation to the pangram classification.
 #[derive(PartialEq, Debug)]
 pub enum PangramStatus {
  NotPangram,
  Pangram,
  PerfectPangram,
 }
 
-/// Function that checks if the slice is a pangram
-///
-/// ## Arguments
-///
-/// * `pangram_str` - the slice that will be checked if is a pangram
-///
-/// ## Examples
+fn compute_letter_counts(pangram_str: &str) -> std::collections::HashMap<char, usize> {
+ let mut letter_counts = std::collections::HashMap::new();
+
+ for ch in pangram_str
+ .to_lowercase()
+ .chars()
+ .filter(|c| c.is_ascii_alphabetic())
+ {
+ *letter_counts.entry(ch).or_insert(0) += 1;
+ }
+
+ letter_counts
+}
+
+/// Determines if the input string is a pangram, and classifies it as either a regular or perfect pangram.
 ///
-/// ```
-/// use the_algorithms_rust::string::is_pangram;
-/// use std::collections::HashSet;
-/// use the_algorithms_rust::string::PangramStatus;
+/// # Arguments
 ///
-/// assert_eq!(
-/// is_pangram("This is not a pangram"),
-/// PangramStatus::NotPangram
-/// );
+/// * `pangram_str` - A reference to the string slice to be checked for pangram status.
 ///
-/// assert_eq!(
-/// is_pangram("The quick brown fox jumps over the lazy dog"),
-/// PangramStatus::Pangram
-/// );
+/// # Returns
 ///
-/// assert_eq!(
-/// is_pangram("Mr. Jock, TV quiz PhD, bags few lynx"),
-/// PangramStatus::PerfectPangram
-/// );
-/// ```
+/// A `PangramStatus` enum indicating whether the string is a pangram, and if so, whether it is a perfect pangram.
 pub fn is_pangram(pangram_str: &str) -> PangramStatus {
- let alphabet: HashSet<char> = "abcdefghijklmnopqrstuvwxyz".chars().collect();
+ let letter_counts = compute_letter_counts(pangram_str);
 
- let letters_used: HashSet<char> = pangram_str
- .to_lowercase()
- .chars()
- .filter(|c| c.is_ascii_alphabetic())
- .collect();
+ let alphabet: HashSet<char> = ('a'..='z').collect();
+ let used_letters: HashSet<_> = letter_counts.keys().cloned().collect();
 
- if letters_used != alphabet {
+ if used_letters != alphabet {
  return PangramStatus::NotPangram;
- };
+ }
 
- if pangram_str.chars().filter(|c| c.is_alphabetic()).count() == alphabet.len() {
+ if letter_counts.values().all(|&count| count == 1) {
  PangramStatus::PerfectPangram
  } else {
  PangramStatus::Pangram
@@ -59,46 +58,35 @@ pub fn is_pangram(pangram_str: &str) -> PangramStatus {
 mod tests {
  use super::*;
 
- #[test]
- fn test_not_pangram() {
- assert_eq!(
- is_pangram("This is not a pangram"),
- PangramStatus::NotPangram
- );
- assert_eq!(is_pangram("today is a good day"), PangramStatus::NotPangram);
- assert_eq!(
- is_pangram(
- "this is almost a pangram but it does not have bcfghjkqwxy and the last letter"
- ),
- PangramStatus::NotPangram
- );
- }
-
- #[test]
- fn test_pangram() {
- assert_eq!(
- is_pangram("The quick brown fox jumps over the lazy dog"),
- PangramStatus::Pangram
- );
- assert_eq!(
- is_pangram("A mad boxer shot a quick, gloved jab to the jaw of his dizzy opponent"),
- PangramStatus::Pangram
- );
- assert_eq!(
- is_pangram("Amazingly few discotheques provide jukeboxes"),
- PangramStatus::Pangram
- );
- assert_eq!(
- is_pangram("How vexingly quick daft zebras jump"),
- PangramStatus::Pangram
- );
+ macro_rules! pangram_tests {
+ ($($name:ident: $tc:expr,)*) => {
+ $(
+ #[test]
+ fn $name() {
+ let (input, expected) = $tc;
+ assert_eq!(is_pangram(input), expected);
+ }
+ )*
+ };
  }
 
- #[test]
- fn test_perfect_pangram() {
- assert_eq!(
- is_pangram("Mr. Jock, TV quiz PhD, bags few lynx"),
- PangramStatus::PerfectPangram
- );
+ pangram_tests! {
+ test_not_pangram_simple: ("This is not a pangram", PangramStatus::NotPangram),
+ test_not_pangram_day: ("today is a good day", PangramStatus::NotPangram),
+ test_not_pangram_almost: ("this is almost a pangram but it does not have bcfghjkqwxy and the last letter", PangramStatus::NotPangram),
+ test_pangram_standard: ("The quick brown fox jumps over the lazy dog", PangramStatus::Pangram),
+ test_pangram_boxer: ("A mad boxer shot a quick, gloved jab to the jaw of his dizzy opponent", PangramStatus::Pangram),
+ test_pangram_discotheques: ("Amazingly few discotheques provide jukeboxes", PangramStatus::Pangram),
+ test_pangram_zebras: ("How vexingly quick daft zebras jump", PangramStatus::Pangram),
+ test_perfect_pangram_jock: ("Mr. Jock, TV quiz PhD, bags few lynx", PangramStatus::PerfectPangram),
+ test_empty_string: ("", PangramStatus::NotPangram),
+ test_repeated_letter: ("aaaaa", PangramStatus::NotPangram),
+ test_non_alphabetic: ("12345!@#$%", PangramStatus::NotPangram),
+ test_mixed_case_pangram: ("ThE QuiCk BroWn FoX JumPs OveR tHe LaZy DoG", PangramStatus::Pangram),
+ test_perfect_pangram_with_symbols: ("Mr. Jock, TV quiz PhD, bags few lynx!", PangramStatus::PerfectPangram),
+ test_long_non_pangram: (&"a".repeat(1000), PangramStatus::NotPangram),
+ test_near_pangram_missing_one_letter: ("The quick brown fox jumps over the lazy do", PangramStatus::NotPangram),
+ test_near_pangram_missing_two_letters: ("The quick brwn f jumps ver the lazy dg", PangramStatus::NotPangram),
+ test_near_pangram_with_special_characters: ("Th3 qu!ck brown f0x jumps 0v3r th3 l@zy d0g.", PangramStatus::NotPangram),
  }
 }