Remove duplicate words

remove_duplicate.rs

// Remove duplicate words
// Your task is to remove all duplicate words from string, leaving only single words entries.
// Example:
// Input:
// 'alpha beta beta gamma gamma gamma delta alpha beta beta gamma gamma gamma delta'
// Output:
// 'alpha beta gamma delta'

fn remove_duplicate_words(s: &str) -> String {
  let r = s.split(" ").fold(String::from(""), |mut r, a| {
      if !r.contains(a) {
         r.push_str(&format!("{} ", a));    
      }
      r
  });
  r.trim().to_string()
} 

#[test]
fn sample_test_cases() {
  assert_eq!(remove_duplicate_words("alpha beta beta gamma gamma gamma delta alpha beta beta gamma gamma gamma delta"), "alpha beta gamma delta");
  assert_eq!(remove_duplicate_words("my cat is my cat fat"), "my cat is fat");
}

Known Issues:

1. String.contains will find any match, will must rewrite methods that check for a complete match.
2. Use type Vec and join() instead type String and push to avoid trim() for result value.