3 files changed, 118 insertions(+), 0 deletions(-)

A day15/Cargo.toml
A day15/input
A day15/src/main.rs

@@ 0,0 1,11 @@
+[package]
+name = "day15"
+version = "0.1.0"
+authors = ["Tomasz Kłak <tomasz@tomaszklak.pl>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+regex = "1"
+lazy_static = "1.4"

@@ 0,0 1,4 @@
+Frosting: capacity 4, durability -2, flavor 0, texture 0, calories 5
+Candy: capacity 0, durability 5, flavor -1, texture 0, calories 8
+Butterscotch: capacity -1, durability 0, flavor 5, texture 0, calories 6
+Sugar: capacity 0, durability 0, flavor -2, texture 2, calories 1

@@ 0,0 1,103 @@
+#[macro_use]
+extern crate lazy_static;
+use regex::Regex;
+use std::io::{BufRead,BufReader};
+use std::collections::HashMap;
+
+lazy_static! {
+    static ref RE : Regex =
+        Regex::new(r"(.+): capacity (.+), durability (.+), flavor (.+), texture (.+), calories (.+)").unwrap();
+}
+
+#[derive(Debug)]
+struct Ingredient {
+    cap: i64,
+    dur: i64,
+    flav: i64,
+    tex: i64,
+    cal: i64
+}
+
+fn parse(s: &str) -> (String, Ingredient) {
+    let c = RE.captures(s).unwrap();
+    (c[1].to_owned(), Ingredient{
+        cap: c[2].parse().unwrap(),
+        dur: c[3].parse().unwrap(),
+        flav: c[4].parse().unwrap(),
+        tex: c[5].parse().unwrap(),
+        cal: c[6].parse().unwrap(),
+    })
+}
+
+fn trunc(v: i64) -> i64 {
+    if v < 0 { 0 } else { v }
+}
+
+fn sum(v: Vec<(i64, &(String, Ingredient))>) -> i64 {
+    let mut cap = 0;
+    let mut dur = 0;
+    let mut flav = 0;
+    let mut tex = 0;
+    for (n, (_, i)) in v.iter() {
+        cap += n * i.cap;
+        dur += n * i.dur;
+        flav += n * i.flav;
+        tex += n * i.tex;
+    }
+    cap = trunc(cap);
+    dur = trunc(dur);
+    flav = trunc(flav);
+    tex = trunc(tex);
+    cap * dur * flav * tex
+}
+
+fn sum2(v: Vec<(i64, &(String, Ingredient))>) -> i64 {
+    let mut cap = 0;
+    let mut dur = 0;
+    let mut flav = 0;
+    let mut tex = 0;
+    let mut cal = 0;
+    for (n, (_, i)) in v.iter() {
+        cap += n * i.cap;
+        dur += n * i.dur;
+        flav += n * i.flav;
+        tex += n * i.tex;
+        cal += n * i.cal;
+    }
+    if cal != 500 {
+        return 0;
+    }
+    cap = trunc(cap);
+    dur = trunc(dur);
+    flav = trunc(flav);
+    tex = trunc(tex);
+    cap * dur * flav * tex
+}
+
+fn main() {
+    let i : Vec<(_, _)> = BufReader::new(std::io::stdin())
+        .lines()
+        .map(|r| parse(&r.unwrap()))
+        .collect();
+    assert_eq!(4, i.len());
+    let mut max = 0;
+    let mut max_with_cap = 0;
+    for a in 0..=100 {
+        for b in 0..=(100-a) {
+            for c in 0..=(100-(a+b)) {
+                let d = 100 - (a+b+c);
+                assert_eq!(100,a+b+c+d);
+                let s = sum(vec![(a, &i[0]), (b, &i[1]), (c, &i[2]), (d, &i[3])]);
+                if s > max {
+                    max = s;
+                }
+                let s = sum2(vec![(a, &i[0]), (b, &i[1]), (c, &i[2]), (d, &i[3])]);
+                if s > max_with_cap {
+                    max_with_cap = s;
+                }
+            }
+        }
+    }
+    println!("{}", max);
+    println!("{}", max_with_cap);
+}