Replace unreachable panics with unreachable!().

source/roman_to_integer/mod.rs

@@ -11,7 +11,7 @@ pub fn roman_to_int(string: String) -> i32 {
       'C' => 100,
       'D' => 500,
       'M' => 1000,
-      _ => panic!("Unknown character: {character}"),
+      _ => unreachable!(),
     };
 
     if let Some(next) = characters.peek() {

source/two_sum/mod.rs

@@ -13,5 +13,5 @@ pub fn two_sum(numbers: Vec<i32>, target: i32) -> Vec<i32> {
     }
   }
 
-  panic!("No pair of numbers found that sum to {}", target)
+  unreachable!()
 }

source/valid_parenthesis/mod.rs

@@ -10,7 +10,7 @@ pub fn is_valid(string: String) -> bool {
       '[' => ']',
       '{' => '}',
       '(' => ')',
-      _ => panic!("Invalid input character: {character}"),
+      _ => unreachable!(),
     }
   }