pub fn capitalize_words_string(words: &[&str]) -> String {
    words.iter()
        .map(|v| capitalize_first(v))
        .collect::<String>()
}
// Step 3.
// Apply the `capitalize_first` function again to a slice of string slices.
// Return a single string.
// ["hello", " ", "world"] -> "Hello World"
Step 3.
Apply the `capitalize_first` function again to a slice of string slices.
Return a single string.
Step 3 . Apply the ` capitalize_first ` function again to a slice of string slices . Return a single string .
pub fn capitalize_words_string(words: &[&str]) -> String {
    words.iter()
        .map(|v| capitalize_first(v))
        .collect::<String>()
}
pub fn capitalize_words_string ( words : & [ & str ] ) -> String { words . iter ( ) . map ( | v | capitalize_first ( v ) ) . collect :: < String > ( ) }
Step 3.
Step 3 .
words
&[&str]
words
&[&str]