Working 2020 day 7

With tests and everything!

Author: romellem

2020/7/README.md

@@ -1,5 +1,71 @@
 # Answers
 
-| Part 1 | Part 2 |
-| ------ | ------ |
-| ` `    | ` `    |
+| Part 1 | Part 2  |
+| ------ | ------- |
+|  `179` | `18925` |
+
+## --- Day 7: Handy Haversacks ---
+
+You land at the regional airport in time for your next flight. In fact, it looks like you'll even have time to grab some food: all flights are currently delayed due to _issues in luggage processing_.
+
+Due to recent aviation regulations, many rules (your puzzle input) are being enforced about bags and their contents; bags must be color-coded and must contain specific quantities of other color-coded bags. Apparently, nobody responsible for these regulations considered how long they would take to enforce!
+
+For example, consider the following rules:
+
+    light red bags contain 1 bright white bag, 2 muted yellow bags.
+    dark orange bags contain 3 bright white bags, 4 muted yellow bags.
+    bright white bags contain 1 shiny gold bag.
+    muted yellow bags contain 2 shiny gold bags, 9 faded blue bags.
+    shiny gold bags contain 1 dark olive bag, 2 vibrant plum bags.
+    dark olive bags contain 3 faded blue bags, 4 dotted black bags.
+    vibrant plum bags contain 5 faded blue bags, 6 dotted black bags.
+    faded blue bags contain no other bags.
+    dotted black bags contain no other bags.
+    
+
+These rules specify the required contents for 9 bag types. In this example, every `faded blue` bag is empty, every `vibrant plum` bag contains 11 bags (5 `faded blue` and 6 `dotted black`), and so on.
+
+You have a _`shiny gold`_ bag. If you wanted to carry it in at least one other bag, how many different bag colors would be valid for the outermost bag? (In other words: how many colors can, eventually, contain at least one `shiny gold` bag?)
+
+In the above rules, the following options would be available to you:
+
+*   A `bright white` bag, which can hold your `shiny gold` bag directly.
+*   A `muted yellow` bag, which can hold your `shiny gold` bag directly, plus some other bags.
+*   A `dark orange` bag, which can hold `bright white` and `muted yellow` bags, either of which could then hold your `shiny gold` bag.
+*   A `light red` bag, which can hold `bright white` and `muted yellow` bags, either of which could then hold your `shiny gold` bag.
+
+So, in this example, the number of bag colors that can eventually contain at least one `shiny gold` bag is _`4`_.
+
+_How many bag colors can eventually contain at least one `shiny gold` bag?_ (The list of rules is quite long; make sure you get all of it.)
+
+-----------------
+
+## --- Part Two ---
+
+It's getting pretty expensive to fly these days - not because of ticket prices, but because of the ridiculous number of bags you need to buy!
+
+Consider again your `shiny gold` bag and the rules from the above example:
+
+*   `faded blue` bags contain `0` other bags.
+*   `dotted black` bags contain `0` other bags.
+*   `vibrant plum` bags contain `11` other bags: 5 `faded blue` bags and 6 `dotted black` bags.
+*   `dark olive` bags contain `7` other bags: 3 `faded blue` bags and 4 `dotted black` bags.
+
+So, a single `shiny gold` bag must contain 1 `dark olive` bag (and the 7 bags within it) plus 2 `vibrant plum` bags (and the 11 bags within _each_ of those): `1 + 1*7 + 2 + 2*11` = _`32`_ bags!
+
+Of course, the actual rules have a small chance of going several levels deeper than this example; be sure to count all of the bags, even if the nesting becomes topologically impractical!
+
+Here's another example:
+
+    shiny gold bags contain 2 dark red bags.
+    dark red bags contain 2 dark orange bags.
+    dark orange bags contain 2 dark yellow bags.
+    dark yellow bags contain 2 dark green bags.
+    dark green bags contain 2 dark blue bags.
+    dark blue bags contain 2 dark violet bags.
+    dark violet bags contain no other bags.
+    
+
+In this example, a single `shiny gold` bag must contain _`126`_ other bags.
+
+_How many individual bags are required inside your single `shiny gold` bag?_

2020/7/bags.js

@@ -3,6 +3,7 @@ const trimEnd = require('lodash/trimEnd');
 class Luggage {
 	constructor(raw_rules) {
 		this.bags_lookup = this.parseToBagsLookup(raw_rules);
+		this.rules = this.parseToRulesLookup(raw_rules);
 	}
 
 	parseToBagsLookup(raw_rules) {
@@ -30,11 +31,58 @@ class Luggage {
 
 		return bags_lookup;
 	}
+
+	parseToRulesLookup(raw_rules) {
+		let bags_lookup = {};
+		for (let rule of raw_rules) {
+			let [parent, children] = rule.split(' bags contain ');
+			if (!bags_lookup[parent]) {
+				bags_lookup[parent] = [];
+			}
+			if (children.includes('no other')) {
+				continue;
+			}
+			children = trimEnd(children, '.').split(', ');
+			for (let child of children) {
+				let [, count, name] = /(\d+) (\w+ \w+) bag/.exec(child);
+				count = parseInt(count, 10);
+				bags_lookup[parent].push(new Bag({ name, count }));
+			}
+		}
+
+		return bags_lookup;
+	}
+
+	countChildrenInside(bag_name) {
+		if (!this.rules[bag_name]) {
+			throw new Error(`Invalid bag name: "${bag_name}"`);
+		}
+
+		let rules = this.rules[bag_name];
+
+		// Early escape, technically isn't necessary but provides base-case clarity on the recursion
+		if (!rules.length) {
+			return 0;
+		}
+
+		let children_count = 0;
+		for (let bag of rules) {
+			let { name, count } = bag;
+			// Add the one bag we are looking at now
+			children_count += count;
+
+			// Plus its children (will be 0 if the child contains no bags itself)
+			children_count += count * this.countChildrenInside(name);
+		}
+
+		return children_count;
+	}
 }
 
 class Bag {
-	constructor({ name }) {
+	constructor({ name, count }) {
 		this.name = name;
+		this.count = count;
 		this.parent_bags = [];
 	}
 

2020/7/input.js

@@ -7,17 +7,34 @@ const input = fs
 	.trim()
 	.split('\n');
 
-const sampleInput = `light red bags contain 1 bright white bag, 2 muted yellow bags.
+const sampleInputs = [
+	{
+		input: `light red bags contain 1 bright white bag, 2 muted yellow bags.
 dark orange bags contain 3 bright white bags, 4 muted yellow bags.
 bright white bags contain 1 shiny gold bag.
 muted yellow bags contain 2 shiny gold bags, 9 faded blue bags.
 shiny gold bags contain 1 dark olive bag, 2 vibrant plum bags.
 dark olive bags contain 3 faded blue bags, 4 dotted black bags.
 vibrant plum bags contain 5 faded blue bags, 6 dotted black bags.
 faded blue bags contain no other bags.
-dotted black bags contain no other bags.`.split('\n');
+dotted black bags contain no other bags.`.split('\n'),
+		partOne: 4,
+		partTwo: 32,
+	},
+	{
+		input: `shiny gold bags contain 2 dark red bags.
+dark red bags contain 2 dark orange bags.
+dark orange bags contain 2 dark yellow bags.
+dark yellow bags contain 2 dark green bags.
+dark green bags contain 2 dark blue bags.
+dark blue bags contain 2 dark violet bags.
+dark violet bags contain no other bags.`.split('\n'),
+		partOne: undefined,
+		partTwo: 126,
+	},
+];
 
 module.exports = {
 	input,
-	sampleInput,
+	sampleInputs,
 };

2020/7/part-one.js

@@ -1,6 +1,15 @@
-const { input, sampleInput } = require('./input');
+const assert = require('assert');
+const { input, sampleInputs } = require('./input');
 const { Luggage } = require('./bags');
 
+for (let sampleInput of sampleInputs) {
+	let sample_luggage = new Luggage(sampleInput.input);
+	let sample_part_one = sample_luggage.bags_lookup['shiny gold'].countUniqueParents();
+	if (sampleInput.partOne !== undefined) {
+		assert.strictEqual(sample_part_one, sampleInput.partOne);
+	}
+}
+
 let luggage = new Luggage(input);
 let shiny_gold = luggage.bags_lookup['shiny gold'];
-console.log(shiny_gold.countUniqueParents());
+console.log(shiny_gold.countUniqueParents());

2020/7/part-two.js

@@ -1 +1,15 @@
-const { input } = require('./input');
+const assert = require('assert');
+const { input, sampleInputs } = require('./input');
+const { Luggage } = require('./bags');
+
+for (let sampleInput of sampleInputs) {
+	let sample_luggage = new Luggage(sampleInput.input);
+	let sample_part_two = sample_luggage.countChildrenInside('shiny gold');
+	if (sampleInput.partTwo !== undefined) {
+		assert.strictEqual(sample_part_two, sampleInput.partTwo);
+	}
+}
+
+let luggage = new Luggage(input);
+let shiny_child_count = luggage.countChildrenInside('shiny gold');
+console.log(shiny_child_count);

README.md

@@ -19,14 +19,15 @@ of manual tinkering.
 
 ## 2020 Puzzles List
 
-Completed: **4 / 25** (16%)
+Completed: **5 / 25** (20%)
 
 *  [✅ Day 1](2020/1/)
 *  [✅ Day 2](2020/2/)
 *  [✅ Day 3](2020/3/)
 *  Day 4
 *  Day 5
 *  [✅ Day 6](2020/6/)
+*  [✅ Day 7](2020/7/)
 
 ## 2019 Puzzles List