2015: day02: finish

aoc2015/src/day02.rs

@@ -0,0 +1,129 @@
+use std::error::Error;
+use std::str::FromStr;
+
+use aoc::err;
+use aoc::Result;
+
+const INPUT: &str = include_str!("../input/day02.txt");
+
+pub fn run() -> Result<()> {
+    let presents: Vec<Present> = INPUT
+        .lines()
+        .map(|line| line.parse())
+        .collect::<Result<_>>()?;
+
+    println!("part 1: {}", part1(&presents));
+    println!("part 2: {}", part2(&presents));
+
+    Ok(())
+}
+
+fn wrapping_paper(present: &Present) -> u64 {
+    let faces_surfaces = &[
+        present.length * present.width,
+        present.width * present.height,
+        present.height * present.length,
+    ];
+
+    let total_area: u64 = faces_surfaces.iter().map(|face| face * 2).sum();
+
+    total_area + faces_surfaces.iter().min().unwrap()
+}
+
+fn part1(presents: &[Present]) -> u64 {
+    presents.iter().map(|p| wrapping_paper(p)).sum()
+}
+
+fn ribbon_bow_length(present: &Present) -> u64 {
+    present.length * present.width * present.height
+}
+
+fn ribbon_needed(present: &Present) -> u64 {
+    let faces_perimeters = &[
+        2 * present.length + 2 * present.width,
+        2 * present.width + 2 * present.height,
+        2 * present.height + 2 * present.length,
+    ];
+
+    let smallest_perimeter = faces_perimeters.iter().min().unwrap();
+
+    smallest_perimeter + ribbon_bow_length(present)
+}
+
+fn part2(presents: &[Present]) -> u64 {
+    presents.iter().map(|p| ribbon_needed(p)).sum()
+}
+
+struct Present {
+    length: u64,
+    width: u64,
+    height: u64,
+}
+
+impl FromStr for Present {
+    type Err = Box<dyn Error>;
+
+    fn from_str(s: &str) -> Result<Self> {
+        let x = s
+            .find('x')
+            .ok_or_else(|| err!("couldn't find first `x` in {}", s))?;
+
+        let length = s[..x].parse()?;
+
+        let s = &s[(x + 1)..];
+        let x = s
+            .find('x')
+            .ok_or_else(|| err!("couldn't find second `x` in {}", s))?;
+
+        let width = s[..x].parse()?;
+
+        let s = &s[(x + 1)..].trim_end();
+
+        let height = s.parse()?;
+
+        Ok(Present {
+            length,
+            width,
+            height,
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn part1_provided() {
+        assert_eq!(wrapping_paper(&"2x3x4".parse().unwrap()), 58);
+        assert_eq!(wrapping_paper(&"1x1x10".parse().unwrap()), 43);
+    }
+
+    #[test]
+    fn part1_real() {
+        let presents: Vec<Present> = INPUT
+            .lines()
+            .map(|line| line.parse())
+            .collect::<Result<_>>()
+            .unwrap();
+
+        assert_eq!(part1(&presents), 1598415);
+    }
+
+    #[test]
+    fn part2_provided() {
+        assert_eq!(ribbon_needed(&"2x3x4".parse().unwrap()), 34);
+        assert_eq!(ribbon_needed(&"1x1x10".parse().unwrap()), 14);
+    }
+
+    #[test]
+    fn part2_real() {
+        let presents: Vec<Present> = INPUT
+            .lines()
+            .map(|line| line.parse())
+            .collect::<Result<_>>()
+            .unwrap();
+
+        assert_eq!(part2(&presents), 3812909);
+    }
+}

aoc2015/src/lib.rs

@@ -1 +1,2 @@
 pub mod day01;
+pub mod day02;

aoc2015/src/main.rs

@@ -1,9 +1,10 @@
 use aoc::Result;
 
 use aoc2015::day01;
+use aoc2015::day02;
 
 fn main() -> Result<()> {
-    let days: &[fn() -> Result<()>] = &[day01::run];
+    let days: &[fn() -> Result<()>] = &[day01::run, day02::run];
 
     aoc::run(days)
 }