rust exercuse: scytale_cipher

subjects/scytale_cipher/README.md

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+## scytale_cipher
+
+### Instructions
+
+Create a function called `scytale_cipher` that takes a `string` and an `integer` and returns a `string`.
+This function should create a scytale cipher also known as spartan cipher. In practice its a cylinder with a
+strip strapped around it on which is written a message, when removed the strip the message is coded.
+Depending on the size of the cylinder the message would change. So the only way to decipher the coded message is
+by using a cylinder of the same size.
+
+You function should recreate the scytale cipher, the string being the message and the size being the number of
+straps in the cylinder.
+
+### Example
+
+message : "scytale Code"
+size : 6
+
+```console
+['s', 'e']
+['c', ' ']
+['y', 'C']
+['t', 'o']
+['a', 'd']
+['l', 'e']
+```
+
+output : sec yCtoadle
+size : 8
+
+```console
+['s', 'C']
+['c', 'o']
+['y', 'd']
+['t', 'e']
+['a', ' ']
+['l', ' ']
+['e', ' ']
+[' ', ' ']
+```
+
+output : sCcoydtea l e
+
+### Expected Functions
+
+```rust
+fn scytale_cipher(message: String, i: u32) -> String {}
+```
+
+### Usage
+
+Here is a program to test your function
+
+```rust
+fn main() {
+    println!("\"scytale Code\" size=6 -> {:?}", scytale_cipher(String::from("scytale Code"), 6)));
+    println!("\"scytale Code\" size=8 -> {:?}", scytale_cipher(String::from("scytale Code"), 8)));
+}
+```
+
+And its output
+
+```console
+student@ubuntu:~/[[ROOT]]/test$ cargo run
+"scytale Code" size=6 -> "sec yCtoadle"
+"scytale Code" size=8 -> "sCcoydtea l e"
+student@ubuntu:~/[[ROOT]]/test$
+```