update shorter code

day2/src/main.rs

@@ -1,9 +1,7 @@
 use std::env;
-use std::fs::File;
-use std::io::BufReader;
-use std::io::BufRead;
+use std::fs;
 
-fn score(line: String) -> i64 {
+fn score(line: &str) -> i64 {
     match line.trim() {
         "A X" => 3 + 0,
         "A Y" => 1 + 3,
@@ -19,13 +17,11 @@ fn score(line: String) -> i64 {
 }
 
 fn main() {
-    let args: Vec<String> = env::args().collect();
-    let input = &args[1];
-    let reader = BufReader::new(File::open(input).expect("where file?"));
+    let input = &env::args().collect::<Vec<String>>()[1];
 
     let mut sum = 0;
-    for line in reader.lines() {
-        sum += score(line.unwrap());
+    for line in fs::read_to_string(input).unwrap().lines() {
+        sum += score(line);
     }
 
     println!("Sum: {}", sum);