Improve Palindrome (#839)

ref: improve palindrome

src/string/palindrome.rs

@@ -1,24 +1,74 @@
+//! A module for checking if a given string is a palindrome.
+
+/// Checks if the given string is a palindrome.
+///
+/// A palindrome is a sequence that reads the same backward as forward.
+/// This function ignores non-alphanumeric characters and is case-insensitive.
+///
+/// # Arguments
+///
+/// * `s` - A string slice that represents the input to be checked.
+///
+/// # Returns
+///
+/// * `true` if the string is a palindrome; otherwise, `false`.
 pub fn is_palindrome(s: &str) -> bool {
-    let mut chars = s.chars();
+    let mut chars = s
+        .chars()
+        .filter(|c| c.is_alphanumeric())
+        .map(|c| c.to_ascii_lowercase());
+
     while let (Some(c1), Some(c2)) = (chars.next(), chars.next_back()) {
         if c1 != c2 {
             return false;
         }
     }
+
     true
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
 
-    #[test]
-    fn palindromes() {
-        assert!(is_palindrome("abcba"));
-        assert!(is_palindrome("abba"));
-        assert!(is_palindrome("a"));
-        assert!(is_palindrome("arcra"));
-        assert!(!is_palindrome("abcde"));
-        assert!(!is_palindrome("aaaabbbb"));
+    macro_rules! palindrome_tests {
+        ($($name:ident: $inputs:expr,)*) => {
+            $(
+                #[test]
+                fn $name() {
+                    let (input, expected) = $inputs;
+                    assert_eq!(is_palindrome(input), expected);
+                }
+            )*
+        }
+    }
+
+    palindrome_tests! {
+        odd_palindrome: ("madam", true),
+        even_palindrome: ("deified", true),
+        single_character_palindrome: ("x", true),
+        single_word_palindrome: ("eye", true),
+        case_insensitive_palindrome: ("RaceCar", true),
+        mixed_case_and_punctuation_palindrome: ("A man, a plan, a canal, Panama!", true),
+        mixed_case_and_space_palindrome: ("No 'x' in Nixon", true),
+        empty_string: ("", true),
+        pompeii_palindrome: ("Roma-Olima-Milo-Amor", true),
+        napoleon_palindrome: ("Able was I ere I saw Elba", true),
+        john_taylor_palindrome: ("Lewd did I live, & evil I did dwel", true),
+        well_know_english_palindrome: ("Never odd or even", true),
+        palindromic_phrase: ("Rats live on no evil star", true),
+        names_palindrome: ("Hannah", true),
+        prime_minister_of_cambodia: ("Lon Nol", true),
+        japanese_novelist_and_manga_writer: ("Nisio Isin", true),
+        actor: ("Robert Trebor", true),
+        rock_vocalist: ("Ola Salo", true),
+        pokemon_species: ("Girafarig", true),
+        lychrel_num_56: ("121", true),
+        universal_palindrome_date: ("02/02/2020", true),
+        french_palindrome: ("une Slave valse nu", true),
+        finnish_palindrome: ("saippuakivikauppias", true),
+        non_palindrome_simple: ("hello", false),
+        non_palindrome_with_punctuation: ("hello!", false),
+        non_palindrome_mixed_case: ("Hello, World", false),
     }
 }