refactor: implemented compiler recommendations

src/main.rs

@@ -1,24 +1,23 @@
 fn main() {
-    let directions = "ENWESWNS".to_string();
+    let directions = "ENWESWNS";
     let res = shorten(directions);
-    println!("{:?}", res);
+    println!("{res}");
 }
 
-fn shorten(directions: String) -> String {
+fn shorten(directions: &str) -> String {
     let characters: Vec<_> = directions.chars().collect();
     let mut result = remove_doubles(&characters);
     loop {
         let out = remove_doubles(&result);
         if out.len() == result.len() {
             break;
-        } else {
+        }
         result = out;
     }
-    }
-    result.iter().map(|f| f.to_string()).collect()
+    result.iter().map(char::to_string).collect()
 }
 
-fn remove_doubles(characters: &Vec<char>) -> Vec<char> {
+fn remove_doubles(characters: &[char]) -> Vec<char> {
     let mut shortenable_map = vec![false; characters.len()];
     let windows = characters.windows(2);
 
@@ -32,17 +31,12 @@ fn remove_doubles(characters: &Vec<char>) -> Vec<char> {
 
     characters
         .iter()
-        .zip(shortenable_map)
-        .filter_map(|(c, shortenable)| if shortenable { None } else { Some(*c) })
+        .enumerate()
+        .filter(|(idx, _)| !shortenable_map[*idx])
+        .map(|(_, itm)| *itm)
         .collect()
 }
 
 fn is_shortenable(chars: &[char]) -> bool {
-    match chars {
-        &['N', 'S'] => true,
-        &['S', 'N'] => true,
-        &['W', 'E'] => true,
-        &['E', 'W'] => true,
-        _ => false,
-    }
+    matches!(*chars, ['N', 'S'] | ['S', 'N'] | ['W', 'E'] | ['E', 'W'])
 }