Improve Lipogram (#821)

ref: improve lipogram

src/string/lipogram.rs

@@ -1,14 +1,25 @@
 use std::collections::HashSet;
 
-/// Function that returns the letters that are missing from the input slice  
-/// and are present in the English alphabet  
+/// Represents possible errors that can occur when checking for lipograms.
+#[derive(Debug, PartialEq, Eq)]
+pub enum LipogramError {
+    /// Indicates that a non-alphabetic character was found in the input.
+    NonAlphabeticCharacter,
+    /// Indicates that a missing character is not in lowercase.
+    NonLowercaseMissingChar,
+}
+
+/// Computes the set of missing alphabetic characters from the input string.
 ///
-/// ## Arguments
+/// # Arguments
 ///
-/// * `in_str` - the slice that will be checked for missing characters
+/// * `in_str` - A string slice that contains the input text.
 ///
+/// # Returns
+///
+/// Returns a `HashSet<char>` containing the lowercase alphabetic characters that are not present in `in_str`.
 fn compute_missing(in_str: &str) -> HashSet<char> {
-    let alphabet: HashSet<char> = "abcdefghijklmnopqrstuvwxyz".chars().collect();
+    let alphabet: HashSet<char> = ('a'..='z').collect();
 
     let letters_used: HashSet<char> = in_str
         .to_lowercase()
@@ -19,75 +30,83 @@ fn compute_missing(in_str: &str) -> HashSet<char> {
     alphabet.difference(&letters_used).cloned().collect()
 }
 
-/// Function that checks if the slice is a lipogram with specific missing letters.  
-/// Lipogram - sentence in which a particular letter or group of letters is avoided
-///
-/// ## Arguments
+/// Checks if the provided string is a lipogram, meaning it is missing specific characters.
 ///
-/// * `lipogram_str` - the slice that will be checked if is a lipogram with specific missing letters
-/// * `missing_chars` - the characters that has to be missing
+/// # Arguments
 ///
-/// ## Examples
+/// * `lipogram_str` - A string slice that contains the text to be checked for being a lipogram.
+/// * `missing_chars` - A reference to a `HashSet<char>` containing the expected missing characters.
 ///
-/// ```
-/// use the_algorithms_rust::string::is_lipogram;
-/// use std::collections::HashSet;
+/// # Returns
 ///
-/// assert!(
-///    !is_lipogram("The quick brown fox jumps over the lazy dog",
-///    &HashSet::from(['x'])
-/// ));
-///
-/// assert!(
-///    is_lipogram("The brown cat jumped over the lazy dog with a brick",
-///    &HashSet::from(['f', 'q', 's', 'x'])
-/// ));
-///
-/// assert!(
-///    !is_lipogram("The quick brown fox jumped over the lazy dog",
-///    &HashSet::from(['x'])
-/// ));
-/// ```
-pub fn is_lipogram(lipogram_str: &str, missing_chars: &HashSet<char>) -> bool {
-    if !missing_chars.iter().all(|&c| c.is_lowercase()) {
-        panic!("missing_chars should be all lowercase.")
+/// Returns `Ok(true)` if the string is a lipogram that matches the provided missing characters,
+/// `Ok(false)` if it does not match, or a `LipogramError` if the input contains invalid characters.
+pub fn is_lipogram(
+    lipogram_str: &str,
+    missing_chars: &HashSet<char>,
+) -> Result<bool, LipogramError> {
+    for &c in missing_chars {
+        if !c.is_lowercase() {
+            return Err(LipogramError::NonLowercaseMissingChar);
+        }
     }
 
-    missing_chars == &compute_missing(lipogram_str)
+    for c in lipogram_str.chars() {
+        if !c.is_ascii_alphabetic() && !c.is_whitespace() {
+            return Err(LipogramError::NonAlphabeticCharacter);
+        }
+    }
+
+    let missing = compute_missing(lipogram_str);
+    Ok(missing == *missing_chars)
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
+
     macro_rules! test_lipogram {
-    ($($name:ident: $inputs:expr,)*) => {
-    $(
-        #[test]
-        fn $name() {
-            let (in_str, missing_chars, other_chars) = $inputs;
-            assert_ne!(missing_chars, other_chars);
-            assert_eq!(compute_missing(in_str), missing_chars);
-            assert!(is_lipogram(in_str, &missing_chars));
-            assert!(!is_lipogram(in_str, &other_chars));
+        ($($name:ident: $tc:expr,)*) => {
+            $(
+                #[test]
+                fn $name() {
+                    let (input, missing_chars, expected) = $tc;
+                    assert_eq!(is_lipogram(input, &missing_chars), expected);
+                }
+            )*
         }
-    )*
     }
-}
 
     test_lipogram! {
-        lipogram1: ("The quick brown fox jumps over the lazy dog", HashSet::from([]), HashSet::from(['a', 'b'])),
-        lipogram2: ("Jackdaws love my big sphinx of quartz", HashSet::from([]), HashSet::from(['x'])),
-        lipogram3: ("abcdefghijklmnopqrstuvwxyz", HashSet::from([]), HashSet::from(['x', 'y', 'z'])),
-        lipogram4: ("Five quacking zephyrs jolt my wax bed", HashSet::from([]), HashSet::from(['a'])),
-        lipogram5: ("The quick brown fox jumped over the lazy dog", HashSet::from(['s']), HashSet::from([])),
-        lipogram6: ("abcdefghijklmnopqrstuvwxy", HashSet::from(['z']), HashSet::from(['y', 'z'])),
-        lipogram7: ("The brown fox jumped over the lazy dog with a brick", HashSet::from(['q', 's']), HashSet::from(['b'])),
-        lipogram8: ("ABCdefghijklmnopqrstuvwx", HashSet::from(['y', 'z']), HashSet::from(['a', 'b'])),
-    }
-
-    #[test]
-    #[should_panic]
-    fn test_is_lipogram_panics_when_missing_chars_are_upper_case() {
-        is_lipogram("abcdefghijklmnopqrstuvwx", &HashSet::from(['y', 'Z']));
+        perfect_pangram: (
+            "The quick brown fox jumps over the lazy dog",
+            HashSet::from([]),
+            Ok(true)
+        ),
+        lipogram_single_missing: (
+            "The quick brown fox jumped over the lazy dog",
+            HashSet::from(['s']),
+            Ok(true)
+        ),
+        lipogram_multiple_missing: (
+            "The brown fox jumped over the lazy dog",
+            HashSet::from(['q', 'i', 'c', 'k', 's']),
+            Ok(true)
+        ),
+        long_lipogram_single_missing: (
+            "A jovial swain should not complain of any buxom fair who mocks his pain and thinks it gain to quiz his awkward air",
+            HashSet::from(['e']),
+            Ok(true)
+        ),
+        invalid_non_lowercase_chars: (
+            "The quick brown fox jumped over the lazy dog",
+            HashSet::from(['X']),
+            Err(LipogramError::NonLowercaseMissingChar)
+        ),
+        invalid_non_alphabetic_input: (
+            "The quick brown fox jumps over the lazy dog 123@!",
+            HashSet::from([]),
+            Err(LipogramError::NonAlphabeticCharacter)
+        ),
     }
 }