Completed day 1

day1/src/main.rs

@@ -0,0 +1,88 @@
+use std::fs::File;
+use std::io::{self, prelude::*, BufReader};
+
+const INPUT: &str = "input/input.txt";
+
+fn read_masses(filename: &str) -> io::Result<Vec<u32>> {
+    let file = File::open(filename)?;
+    let reader = BufReader::new(file);
+
+    Ok(reader
+        .lines()
+        .map(|mass| mass.unwrap().parse().unwrap())
+        .collect())
+}
+
+fn calculate_fuel_requirement(mass: u32) -> u32 {
+    mass / 3 - 2
+}
+
+fn calculate_fuel_requirement_including_fuel_mass(mass: u32) -> u32 {
+    let mut fuel: i32 = mass as i32 / 3 - 2;
+    let mut total_requirement = 0;
+
+    while fuel > 0 {
+        total_requirement += fuel as u32;
+        fuel = fuel / 3 - 2;
+    }
+
+    total_requirement
+}
+
+fn calculate_fuel_sum(masses: Vec<u32>) -> u32 {
+    let fuel_requirements: Vec<u32> = masses
+        .iter()
+        .map(|mass| calculate_fuel_requirement(*mass))
+        .collect();
+    fuel_requirements.iter().sum()
+}
+
+fn calculate_fuel_sum_including_fuel_mass(masses: Vec<u32>) -> u32 {
+    let fuel_requirements: Vec<u32> = masses
+        .iter()
+        .map(|mass| calculate_fuel_requirement_including_fuel_mass(*mass))
+        .collect();
+    fuel_requirements.iter().sum()
+}
+
+fn solve_part1() -> io::Result<u32> {
+    Ok(calculate_fuel_sum(read_masses(INPUT)?))
+}
+
+fn solve_part2() -> io::Result<u32> {
+    Ok(calculate_fuel_sum_including_fuel_mass(read_masses(INPUT)?))
+}
+
+fn main() -> io::Result<()> {
+    println!("Part 1: {}", solve_part1()?);
+    println!("Part 2: {}", solve_part2()?);
+
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const TEST_INPUT: &str = "input/test.txt";
+
+    #[test]
+    fn reads_masses() {
+        assert_eq!(read_masses(TEST_INPUT).unwrap(), vec![12, 14, 1969, 100756]);
+    }
+
+    #[test]
+    fn calculates_correct_fuel_requirements() {
+        assert_eq!(calculate_fuel_requirement(12), 2);
+        assert_eq!(calculate_fuel_requirement(14), 2);
+        assert_eq!(calculate_fuel_requirement(1969), 654);
+        assert_eq!(calculate_fuel_requirement(100756), 33583);
+    }
+
+    #[test]
+    fn calculates_correct_fuel_requirements_including_fuel_mass() {
+        assert_eq!(calculate_fuel_requirement_including_fuel_mass(14), 2);
+        assert_eq!(calculate_fuel_requirement_including_fuel_mass(1969), 966);
+        assert_eq!(calculate_fuel_requirement_including_fuel_mass(100756), 50346);
+    }
+}