Year 2015 Day 15

Author: maneatingape

README.md

@@ -250,3 +250,4 @@ pie
 | 12 | [JSAbacusFramework.io](https://adventofcode.com/2015/day/12) | [Source](src/year2015/day12.rs) | 80 |
 | 13 | [Knights of the Dinner Table](https://adventofcode.com/2015/day/13) | [Source](src/year2015/day13.rs) | 39 |
 | 14 | [Reindeer Olympics](https://adventofcode.com/2015/day/14) | [Source](src/year2015/day14.rs) | 28 |
+| 15 | [Science for Hungry People](https://adventofcode.com/2015/day/15) | [Source](src/year2015/day15.rs) | 41 |

benches/benchmark.rs

@@ -50,6 +50,7 @@ mod year2015 {
     benchmark!(year2015, day12);
     benchmark!(year2015, day13);
     benchmark!(year2015, day14);
+    benchmark!(year2015, day15);
 }
 
 mod year2019 {

input/year2015/day15.txt

@@ -0,0 +1,4 @@
+Sugar: capacity 3, durability 0, flavor 0, texture -3, calories 2
+Sprinkles: capacity -3, durability 3, flavor 0, texture 0, calories 9
+Candy: capacity -1, durability 0, flavor 4, texture 0, calories 1
+Chocolate: capacity 0, durability 0, flavor -2, texture 2, calories 8

src/lib.rs

@@ -174,6 +174,7 @@ pub mod year2015 {
     pub mod day12;
     pub mod day13;
     pub mod day14;
+    pub mod day15;
 }
 
 /// # Rescue Santa from deep space with a solar system adventure.

src/main.rs

@@ -90,6 +90,7 @@ fn all_solutions() -> Vec<Solution> {
         solution!(year2015, day12),
         solution!(year2015, day13),
         solution!(year2015, day14),
+        solution!(year2015, day15),
         // 2019
         solution!(year2019, day01),
         solution!(year2019, day02),

src/year2015/day15.rs

@@ -0,0 +1,58 @@
+//! # Science for Hungry People
+//!
+//! Brute force solution trying every possible combination of ingredients. The loop conditions are
+//! calculated so that the ingredients always sum to 100. Solves part one and two simultaneously.
+//!
+//! As an optimization we check halfway through the loops to see if any ingredient will never be
+//! be greater than zero to skip large numbers of combinations.
+use crate::util::iter::*;
+use crate::util::parse::*;
+use std::array::from_fn;
+
+type Ingredient = [i32; 5];
+type Input = (i32, i32);
+
+pub fn parse(input: &str) -> Input {
+    let recipe: Vec<Ingredient> = input.iter_signed().chunk::<5>().collect();
+    let mut part_one = 0;
+    let mut part_two = 0;
+
+    for a in 0..101 {
+        let first: Ingredient = from_fn(|i| a * recipe[0][i]);
+
+        for b in 0..(101 - a) {
+            let second: Ingredient = from_fn(|i| first[i] + b * recipe[1][i]);
+
+            // Check if any ingredient can never be greater than zero.
+            let check: Ingredient =
+                from_fn(|i| second[i] + recipe[2][i].max(recipe[3][i]) * (100 - a - b));
+            if check.iter().any(|&n| n <= 0) {
+                continue;
+            }
+
+            for c in 0..(101 - a - b) {
+                let d = 100 - a - b - c;
+                let third: Ingredient = from_fn(|i| second[i] + c * recipe[2][i]);
+                let fourth: Ingredient = from_fn(|i| third[i] + d * recipe[3][i]);
+
+                let score = fourth.iter().take(4).map(|&n| n.max(0)).product();
+                let calories = fourth[4];
+
+                part_one = part_one.max(score);
+                if calories == 500 {
+                    part_two = part_two.max(score);
+                }
+            }
+        }
+    }
+
+    (part_one, part_two)
+}
+
+pub fn part1(input: &Input) -> i32 {
+    input.0
+}
+
+pub fn part2(input: &Input) -> i32 {
+    input.1
+}

tests/test.rs

@@ -43,6 +43,7 @@ mod year2015 {
     mod day12_test;
     mod day13_test;
     mod day14_test;
+    mod day15_test;
 }
 
 mod year2019 {

tests/year2015/day15_test.rs

@@ -0,0 +1,19 @@
+use aoc::year2015::day15::*;
+
+const EXAMPLE: &str = "\
+Butterscotch: capacity -1, durability -2, flavor 6, texture 3, calories 8
+Cinnamon: capacity 2, durability 3, flavor -2, texture -1, calories 3
+Filler 1: capacity -200, durability -300, flavor -600, texture -300, calories 0
+Filler 2: capacity -200, durability -300, flavor -600, texture -300, calories 0";
+
+#[test]
+fn part1_test() {
+    let input = parse(EXAMPLE);
+    assert_eq!(part1(&input), 62842880);
+}
+
+#[test]
+fn part2_test() {
+    let input = parse(EXAMPLE);
+    assert_eq!(part2(&input), 57600000);
+}