Solve day 1 puzzle 2

src/day_1/puzzle_2.rs

@@ -1,3 +1,37 @@
+use std::fs::File;
+use std::io::{BufRead, BufReader};
+use std::path::Path;
+
 pub fn solve() {
-    println!("NYI");
+    let masses = read_masses("./src/day_1/puzzle_1.txt");
+    let mut sum: f32 = 0.0;
+
+    for mass in masses {
+        sum += calc_fuel_req(mass, 0.0);
+    }
+    println!("sum: {}", sum);
+}
+
+fn calc_fuel_req(mass: f32, total: f32) -> f32 {
+    let fuel_req = (mass / 3.0).floor() - 2.0;
+
+    if fuel_req > 0.0 {
+        calc_fuel_req(fuel_req, total + fuel_req)
+    } else {
+        total
+    }
+}
+
+fn read_masses(filename: impl AsRef<Path>) -> Vec<f32> {
+    let file = File::open(filename).expect("no such file");
+    let buffer = BufReader::new(file);
+
+    buffer
+        .lines()
+        .map(|l| {
+            l.expect("could not read line")
+                .parse::<f32>()
+                .expect("could not parse line")
+        })
+        .collect()
 }