finish clippy

exercises/clippy/clippy1.rs

@@ -11,10 +11,10 @@
 
 // I AM NOT DONE
 
-use std::f32;
+use std::f32::consts;
 
 fn main() {
-    let pi = 3.14f32;
+    let pi = consts::PI;
     let radius = 5.00f32;
 
     let area = pi * f32::powi(radius, 2);

exercises/clippy/clippy2.rs

@@ -1,5 +1,5 @@
 // clippy2.rs
-// 
+//
 // Execute `rustlings hint clippy2` or use the `hint` watch subcommand for a
 // hint.
 
@@ -8,7 +8,7 @@
 fn main() {
     let mut res = 42;
     let option = Some(12);
-    for x in option {
+    if let Some(x) = option {
         res += x;
     }
     println!("{}", res);

exercises/clippy/clippy3.rs

@@ -1,30 +1,26 @@
 // clippy3.rs
-// 
+//
 // Here's a couple more easy Clippy fixes, so you can see its utility.
 // No hints.
 
 // I AM NOT DONE
 
 #[allow(unused_variables, unused_assignments)]
 fn main() {
-    let my_option: Option<()> = None;
-    if my_option.is_none() {
-        my_option.unwrap();
+    let my_option: Option<()> = Some(());
+    if let Some(x) = my_option {
+        println!("fuck");
     }
-
-    let my_arr = &[
-        -1, -2, -3
-        -4, -5, -6
-    ];
+    let my_arr = &[-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];
     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 b: {}", value_a, value_b);
 }