feat: 🎸 added solutions for lifetime exercises

exercises/lifetimes/lifetimes1.rs

@@ -7,9 +7,7 @@
 //
 // Execute `rustlings hint lifetimes1` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
+fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
-
-fn longest(x: &str, y: &str) -> &str {
     if x.len() > y.len() {
         x
     } else {

exercises/lifetimes/lifetimes2.rs

@@ -6,8 +6,6 @@
 //
 // Execute `rustlings hint lifetimes2` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
     if x.len() > y.len() {
         x
@@ -18,10 +16,9 @@ fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
 
 fn main() {
     let string1 = String::from("long string is long");
-    let result;
     {
         let string2 = String::from("xyz");
-        result = longest(string1.as_str(), string2.as_str());
+        let result = longest(string1.as_str(), string2.as_str());
+        println!("The longest string is '{}'", result);
     }
-    println!("The longest string is '{}'", result);
 }

exercises/lifetimes/lifetimes3.rs

@@ -4,17 +4,18 @@
 //
 // Execute `rustlings hint lifetimes3` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
+struct Book<'a> {
-
+    author: &'a str,
-struct Book {
+    title: &'a str,
-    author: &str,
-    title: &str,
 }
 
 fn main() {
     let name = String::from("Jill Smith");
     let title = String::from("Fish Flying");
-    let book = Book { author: &name, title: &title };
+    let book = Book {
+        author: &name,
+        title: &title,
+    };
 
     println!("{} by {}", book.title, book.author);
 }