Solve valid-palindrome.

source/lib.rs

@@ -9,4 +9,5 @@ pub mod reverse_integer;
 pub mod roman_to_integer;
 pub mod two_sum;
 pub mod valid_anagram;
+pub mod valid_palindrome;
 pub mod valid_parenthesis;

source/valid_palindrome/mod.rs

@@ -0,0 +1,14 @@
+pub fn is_palindrome(string: String) -> bool {
+  let normalized = string.chars().filter_map(|c| {
+    if char::is_alphanumeric(c) {
+      Some(c.to_ascii_lowercase())
+    } else {
+      None
+    }
+  });
+
+  let regular = normalized.clone().collect::<String>();
+  let reversed = normalized.rev().collect::<String>();
+
+  regular == reversed
+}

tests/valid_palindrome.rs

@@ -0,0 +1,11 @@
+use leetcode::valid_palindrome::is_palindrome;
+
+use test_case::test_case;
+
+#[test_case("A man, a plan, a canal: Panama", true; "valid")]
+#[test_case("race a car", false; "invalid")]
+#[test_case("", true; "empty")]
+#[test_case(" \t", true; "whitespace only")]
+fn test_valid_palindrome(input: &str, expected: bool) {
+  assert_eq!(is_palindrome(input.to_string()), expected);
+}