did hello world and guessing game.

the_book/guessing_game/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "guessing_game"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+rand="0.8.3"

the_book/guessing_game/src/main.rs

@@ -0,0 +1,35 @@
+use std::io;
+use std::cmp::Ordering;
+use rand::Rng;
+
+fn main() {
+    println!("guess the number!");
+
+    let secret_number = rand::thread_rng().gen_range(1..101);
+
+    println!("The secret number is: {}", secret_number);
+
+    loop{
+        println!("input your guess:");
+
+        let mut guess = String::new();
+
+        io::stdin().read_line(&mut guess).expect("failed to read line");
+
+        println!("you guessed: {}", guess);
+
+        let guess: u32 = match guess.trim().parse(){
+            Ok(num) => num,
+            Err(_)=>continue,
+        };
+
+        match guess.cmp(&secret_number){
+            Ordering::Less=>println!("too small!"),
+            Ordering::Equal=>{
+                println!("you win!");
+                break;
+            }
+            Ordering::Greater=>println!("too big!")
+        }
+    }
+}