227 lines
5.8 KiB
Rust
227 lines
5.8 KiB
Rust
use std::cmp::Ordering;
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use std::collections::HashMap;
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use std::fmt::Write;
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use anyhow::{Context, Result};
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const INPUT: &str = include_str!("../input/day14.txt");
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pub fn run() -> Result<String> {
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let mut res = String::with_capacity(128);
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writeln!(res, "part 1: {}", part1(INPUT)?)?;
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writeln!(res, "part 2: {}", part2(INPUT)?)?;
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Ok(res)
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}
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fn parse_recipes(input: &str) -> Result<HashMap<String, Recipe>> {
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let mut recipes = HashMap::new();
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for line in input.lines() {
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let arrow = line
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.find(" => ")
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.with_context(|| format!("couldn't find arrow in line: {}", line))?;
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let elems = &line[..arrow];
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let elems = elems
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.split(", ")
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.map(|elem| {
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let space = elem
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.find(' ')
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.with_context(|| format!("couldn't find separator for elem {}", elem))?;
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let amount = elem[..space].parse()?;
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let name = &elem[(space + 1)..];
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Ok(RecipeElem {
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name: name.to_string(),
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amount,
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})
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})
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.collect::<Result<Vec<_>>>()?;
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let result = &line[(arrow + 4)..].trim_end();
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let space = result
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.find(' ')
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.with_context(|| format!("couldn't find separator for result {}", result))?;
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let result_amount = result[..space].parse()?;
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let result_name = &result[(space + 1)..];
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recipes.insert(
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result_name.to_string(),
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Recipe {
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produced: result_amount,
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elems,
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},
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);
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}
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Ok(recipes)
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}
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fn get_ore_cost(
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material: String,
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quantity: u64,
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recipes: &HashMap<String, Recipe>,
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inventory: &mut HashMap<String, u64>,
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) -> Result<u64> {
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if material == "ORE" {
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return Ok(quantity);
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}
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let mut total = 0;
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let mut in_stock = *inventory.entry(material.clone()).or_default();
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if in_stock < quantity {
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let recipe = recipes
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.get(&material)
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.with_context(|| format!("couldn't find recipe for {}", material))?;
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let needed = quantity - in_stock;
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let num_reactions = (needed + recipe.produced - 1) / recipe.produced;
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for elem in &recipe.elems {
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total += get_ore_cost(
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elem.name.clone(),
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elem.amount * num_reactions,
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recipes,
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inventory,
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)?;
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}
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in_stock += num_reactions * recipe.produced;
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}
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inventory.insert(material, in_stock - quantity);
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Ok(total)
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}
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fn part1(input: &str) -> Result<u64> {
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let recipes = parse_recipes(input)?;
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let mut inventory = HashMap::new();
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get_ore_cost("FUEL".to_string(), 1, &recipes, &mut inventory)
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}
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fn part2(input: &str) -> Result<u64> {
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let mut begin: u64 = 0;
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let mut end: u64 = 1_000_000_000_000;
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let recipes = parse_recipes(input)?;
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while begin <= end {
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let mid = begin + (end - begin) / 2;
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let mut inventory = HashMap::new();
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let ore_cost = get_ore_cost("FUEL".to_string(), mid, &recipes, &mut inventory)?;
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match ore_cost.cmp(&1_000_000_000_000) {
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Ordering::Greater => end = mid - 1,
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Ordering::Less => begin = mid + 1,
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Ordering::Equal => return Ok(mid),
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}
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}
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Ok(end)
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}
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struct RecipeElem {
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name: String,
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amount: u64,
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}
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struct Recipe {
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produced: u64,
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elems: Vec<RecipeElem>,
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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const PROVIDED1: &str = "10 ORE => 10 A
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1 ORE => 1 B
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7 A, 1 B => 1 C
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7 A, 1 C => 1 D
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7 A, 1 D => 1 E
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7 A, 1 E => 1 FUEL
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";
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const PROVIDED2: &str = "9 ORE => 2 A
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8 ORE => 3 B
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7 ORE => 5 C
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3 A, 4 B => 1 AB
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5 B, 7 C => 1 BC
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4 C, 1 A => 1 CA
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2 AB, 3 BC, 4 CA => 1 FUEL
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";
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const PROVIDED3: &str = "157 ORE => 5 NZVS
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165 ORE => 6 DCFZ
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44 XJWVT, 5 KHKGT, 1 QDVJ, 29 NZVS, 9 GPVTF, 48 HKGWZ => 1 FUEL
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12 HKGWZ, 1 GPVTF, 8 PSHF => 9 QDVJ
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179 ORE => 7 PSHF
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177 ORE => 5 HKGWZ
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7 DCFZ, 7 PSHF => 2 XJWVT
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165 ORE => 2 GPVTF
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3 DCFZ, 7 NZVS, 5 HKGWZ, 10 PSHF => 8 KHKGT
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";
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const PROVIDED4: &str = "2 VPVL, 7 FWMGM, 2 CXFTF, 11 MNCFX => 1 STKFG
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17 NVRVD, 3 JNWZP => 8 VPVL
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53 STKFG, 6 MNCFX, 46 VJHF, 81 HVMC, 68 CXFTF, 25 GNMV => 1 FUEL
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22 VJHF, 37 MNCFX => 5 FWMGM
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139 ORE => 4 NVRVD
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144 ORE => 7 JNWZP
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5 MNCFX, 7 RFSQX, 2 FWMGM, 2 VPVL, 19 CXFTF => 3 HVMC
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5 VJHF, 7 MNCFX, 9 VPVL, 37 CXFTF => 6 GNMV
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145 ORE => 6 MNCFX
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1 NVRVD => 8 CXFTF
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1 VJHF, 6 MNCFX => 4 RFSQX
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176 ORE => 6 VJHF
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";
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const PROVIDED5: &str = "171 ORE => 8 CNZTR
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7 ZLQW, 3 BMBT, 9 XCVML, 26 XMNCP, 1 WPTQ, 2 MZWV, 1 RJRHP => 4 PLWSL
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114 ORE => 4 BHXH
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14 VRPVC => 6 BMBT
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6 BHXH, 18 KTJDG, 12 WPTQ, 7 PLWSL, 31 FHTLT, 37 ZDVW => 1 FUEL
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6 WPTQ, 2 BMBT, 8 ZLQW, 18 KTJDG, 1 XMNCP, 6 MZWV, 1 RJRHP => 6 FHTLT
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15 XDBXC, 2 LTCX, 1 VRPVC => 6 ZLQW
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13 WPTQ, 10 LTCX, 3 RJRHP, 14 XMNCP, 2 MZWV, 1 ZLQW => 1 ZDVW
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5 BMBT => 4 WPTQ
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189 ORE => 9 KTJDG
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1 MZWV, 17 XDBXC, 3 XCVML => 2 XMNCP
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12 VRPVC, 27 CNZTR => 2 XDBXC
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15 KTJDG, 12 BHXH => 5 XCVML
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3 BHXH, 2 VRPVC => 7 MZWV
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121 ORE => 7 VRPVC
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7 XCVML => 6 RJRHP
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5 BHXH, 4 VRPVC => 5 LTCX
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";
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#[test]
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fn part1_provided() {
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assert_eq!(part1(PROVIDED1).unwrap(), 31);
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assert_eq!(part1(PROVIDED2).unwrap(), 165);
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assert_eq!(part1(PROVIDED3).unwrap(), 13312);
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assert_eq!(part1(PROVIDED4).unwrap(), 180697);
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assert_eq!(part1(PROVIDED5).unwrap(), 2210736);
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}
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#[test]
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fn part1_real() {
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assert_eq!(part1(INPUT).unwrap(), 532506);
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}
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#[test]
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fn part2_provided() {
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assert_eq!(part2(PROVIDED3).unwrap(), 82892753);
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assert_eq!(part2(PROVIDED4).unwrap(), 5586022);
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assert_eq!(part2(PROVIDED5).unwrap(), 460664);
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}
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#[test]
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fn part2_real() {
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assert_eq!(part2(INPUT).unwrap(), 2595245);
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}
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}
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