finish iterators2

exercises/iterators/iterators2.rs

@@ -15,7 +15,9 @@ pub fn capitalize_first(input: &str) -> String {
     let mut c = input.chars();
     match c.next() {
         None => String::new(),
-        Some(first) => ???,
+        Some(first) => {
+            first.to_uppercase().to_string() + c.as_str()
+        }
     }
 }
 
@@ -24,15 +26,15 @@ pub fn capitalize_first(input: &str) -> String {
 // Return a vector of strings.
 // ["hello", "world"] -> ["Hello", "World"]
 pub fn capitalize_words_vector(words: &[&str]) -> Vec<String> {
-    vec![]
+    words.iter().map(|word| capitalize_first(word)).collect()
 }
 
 // Step 3.
 // Apply the `capitalize_first` function again to a slice of string slices.
 // Return a single string.
 // ["hello", " ", "world"] -> "Hello World"
 pub fn capitalize_words_string(words: &[&str]) -> String {
-    String::new()
+    words.iter().map(|word| capitalize_first(word)).collect()
 }
 
 #[cfg(test)]