feat: completed solutions

exercises/22_clippy/clippy1.rs

@@ -6,7 +6,7 @@
 
 fn main() {
     // TODO: Fix the Clippy lint in this line.
-    let pi = 3.14;
+    let pi = std::f32::consts::PI;
     let radius: f32 = 5.0;
 
     let area = pi * radius.powi(2);

exercises/22_clippy/clippy2.rs

@@ -1,8 +1,9 @@
 fn main() {
     let mut res = 42;
     let option = Some(12);
+
     // TODO: Fix the Clippy lint.
-    for x in option {
+    if let Some(x) = option {
         res += x;
     }
 

exercises/22_clippy/clippy3.rs

@@ -7,23 +7,23 @@ fn main() {
     let my_option: Option<&str> = None;
     // Assume that you don't know the value of `my_option`.
     // In the case of `Some`, we want to print its value.
-    if my_option.is_none() {
-        println!("{}", my_option.unwrap());
+    if let Some(my_option) = my_option {
+        println!("{}", my_option);
     }
 
     let my_arr = &[
-        -1, -2, -3
+        -1, -2, -3,
         -4, -5, -6
     ];
     println!("My array! Here it is: {my_arr:?}");
 
-    let my_empty_vec = vec![1, 2, 3, 4, 5].resize(0, 5);
+    let my_empty_vec = ();
+    vec![1, 2, 3, 4, 5].resize(0, 5);
     println!("This Vec is empty, see? {my_empty_vec:?}");
 
     let mut value_a = 45;
     let mut value_b = 66;
     // Let's swap these two!
-    value_a = value_b;
-    value_b = value_a;
+    std::mem::swap(&mut value_a, &mut value_b);
     println!("value a: {value_a}; value b: {value_b}");
 }