Solve length-of-last-word.

source/length_of_last_word/mod.rs

@@ -0,0 +1,17 @@
+pub fn length_of_last_word(string: String) -> i32 {
+  string
+    .split_whitespace()
+    .last()
+    .map(|word| word.len())
+    .unwrap_or_default() as i32
+}
+
+#[test]
+fn test_length_of_last_word() {
+  assert_eq!(length_of_last_word("Hello World".to_string()), 5);
+  assert_eq!(
+    length_of_last_word("   fly me   to   the moon  ".to_string()),
+    4
+  );
+  assert_eq!(length_of_last_word("luffy is still joyboy".to_string()), 6);
+}

source/lib.rs

@@ -1,4 +1,5 @@
 pub mod implement_strstr;
+pub mod length_of_last_word;
 pub mod longest_common_prefix;
 pub mod palindrome_number;
 pub mod plus_one;