Update Exercises Directory Names to Reflect Order

exercises/22_clippy/README.md

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+# Clippy
+
+The Clippy tool is a collection of lints to analyze your code so you can catch common mistakes and improve your Rust code.
+
+If you used the installation script for Rustlings, Clippy should be already installed.
+If not you can install it manually via `rustup component add clippy`.
+
+## Further information
+
+- [GitHub Repository](https://github.com/rust-lang/rust-clippy).

exercises/22_clippy/clippy1.rs

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+// clippy1.rs
+//
+// The Clippy tool is a collection of lints to analyze your code so you can
+// catch common mistakes and improve your Rust code.
+//
+// For these exercises the code will fail to compile when there are clippy
+// warnings check clippy's suggestions from the output to solve the exercise.
+//
+// Execute `rustlings hint clippy1` or use the `hint` watch subcommand for a
+// hint.
+
+// I AM NOT DONE
+
+use std::f32;
+
+fn main() {
+    let pi = 3.14f32;
+    let radius = 5.00f32;
+
+    let area = pi * f32::powi(radius, 2);
+
+    println!(
+        "The area of a circle with radius {:.2} is {:.5}!",
+        radius, area
+    )
+}

exercises/22_clippy/clippy2.rs

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+// clippy2.rs
+// 
+// Execute `rustlings hint clippy2` or use the `hint` watch subcommand for a
+// hint.
+
+// I AM NOT DONE
+
+fn main() {
+    let mut res = 42;
+    let option = Some(12);
+    for x in option {
+        res += x;
+    }
+    println!("{}", res);
+}

exercises/22_clippy/clippy3.rs

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+// 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_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);
+    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;
+    println!("value a: {}; value b: {}", value_a, value_b);
+}