strings and modules

exercises/09_strings/strings3.rs

@@ -1,13 +1,15 @@
 fn trim_me(input: &str) -> &str {
-    // TODO: Remove whitespace from both ends of a string.
+    input.trim()
 }
 
 fn compose_me(input: &str) -> String {
-    // TODO: Add " world!" to the string! There are multiple ways to do this.
+    let mut tmp = input.to_string();
+    tmp.push_str(" world!");
+    tmp
 }
 
 fn replace_me(input: &str) -> String {
-    // TODO: Replace "cars" in the string with "balloons".
+    input.replace("cars", "balloons")
 }
 
 fn main() {