add compare.

src/main.rs

@@ -1,3 +1,4 @@
+use std::cmp::Ordering;
 use std::io;
 use rand::Rng;
 
@@ -13,5 +14,14 @@ fn main() {
     io::stdin().read_line(&mut guess_number)
         .expect("Failed to read line.");
 
-    println!("You guess : {:?}", guess_number)
+    let guess_number: u32 = guess_number.trim().parse()
+        .expect("Not a number.");
+
+    println!("You guess : {:?}", guess_number);
+
+    match guess_number.cmp(&secret_number) {
+        Ordering::Less => println!("Too small."),
+        Ordering::Greater => println!("Too big."),
+        Ordering::Equal => println!("You win!")
+    }
 }