Add custom error types HammingDistanceError (#780)

ref: add custom error types `HammingDistanceError`

src/string/hamming_distance.rs

@@ -1,13 +1,24 @@
-pub fn hamming_distance(string_a: &str, string_b: &str) -> usize {
+/// Error type for Hamming distance calculation.
+#[derive(Debug, PartialEq)]
+pub enum HammingDistanceError {
+    InputStringsHaveDifferentLength,
+}
+
+/// Calculates the Hamming distance between two strings.
+///
+/// The Hamming distance is defined as the number of positions at which the corresponding characters of the two strings are different.
+pub fn hamming_distance(string_a: &str, string_b: &str) -> Result<usize, HammingDistanceError> {
     if string_a.len() != string_b.len() {
-        panic!("Strings must have the same length");
+        return Err(HammingDistanceError::InputStringsHaveDifferentLength);
     }
 
-    string_a
+    let distance = string_a
         .chars()
         .zip(string_b.chars())
         .filter(|(a, b)| a != b)
-        .count()
+        .count();
+
+    Ok(distance)
 }
 
 #[cfg(test)]
@@ -16,30 +27,31 @@ mod tests {
 
     macro_rules! test_hamming_distance {
         ($($name:ident: $tc:expr,)*) => {
-        $(
-            #[test]
-            fn $name() {
-                let (str_a, str_b, expected) = $tc;
-                assert_eq!(hamming_distance(str_a, str_b), expected);
-                assert_eq!(hamming_distance(str_b, str_a), expected);
-            }
-        )*
+            $(
+                #[test]
+                fn $name() {
+                    let (str_a, str_b, expected) = $tc;
+                    assert_eq!(hamming_distance(str_a, str_b), expected);
+                    assert_eq!(hamming_distance(str_b, str_a), expected);
+                }
+            )*
         }
     }
 
     test_hamming_distance! {
-        empty_inputs: ("", "", 0),
-        length_1_inputs: ("a", "a", 0),
-        same_strings: ("rust", "rust", 0),
-        regular_input_0: ("karolin", "kathrin", 3),
-        regular_input_1: ("kathrin", "kerstin", 4),
-        regular_input_2: ("00000", "11111", 5),
-        different_case: ("x", "X", 1),
-    }
-
-    #[test]
-    #[should_panic]
-    fn panic_when_inputs_are_of_different_length() {
-        hamming_distance("0", "");
+        empty_inputs: ("", "", Ok(0)),
+        different_length: ("0", "", Err(HammingDistanceError::InputStringsHaveDifferentLength)),
+        length_1_inputs_identical: ("a", "a", Ok(0)),
+        length_1_inputs_different: ("a", "b", Ok(1)),
+        same_strings: ("rust", "rust", Ok(0)),
+        regular_input_0: ("karolin", "kathrin", Ok(3)),
+        regular_input_1: ("kathrin", "kerstin", Ok(4)),
+        regular_input_2: ("00000", "11111", Ok(5)),
+        different_case: ("x", "X", Ok(1)),
+        strings_with_no_common_chars: ("abcd", "wxyz", Ok(4)),
+        long_strings_one_diff: (&"a".repeat(1000), &("a".repeat(999) + "b"), Ok(1)),
+        long_strings_many_diffs: (&("a".repeat(500) + &"b".repeat(500)), &("b".repeat(500) + &"a".repeat(500)), Ok(1000)),
+        strings_with_special_chars_identical: ("!@#$%^", "!@#$%^", Ok(0)),
+        strings_with_special_chars_diff: ("!@#$%^", "&*()_+", Ok(6)),
     }
 }