Add day 7 part2

Author: lundgren2

src/2020/_dayx/test.spec.ts

@@ -1,6 +1,7 @@
-import {part1} from './part1';
 import {readInput} from '../../utils';
 
+import {part1} from './part1';
+
 describe('Advent of Code 2020 - Day x', () => {
   let input: string;
   beforeAll(async () => {

src/2020/day7/part1.ts

@@ -2,7 +2,7 @@ type Bags = Record<string, string[]>;
 
 const parseColor = (rule: string) => rule.replace(/\d|bag(s?.)?/g, '').trim();
 
-const parseBags = (input: string): Bags => {
+export const parseBags = (input: string): Bags => {
   return input.split('\n').reduce((bags, r) => {
     const [, color, rules] = r.match(/([a-z]+ [a-z]+) bags contain (.*)/)!;
     return {...bags, [color]: rules.split(', ')};

src/2020/day7/part2.ts

@@ -0,0 +1,32 @@
+import {parseBags} from './part1';
+
+const parseAmount = (rule: string) => Number(rule.match(/\d/));
+const parseColor = (rule: string) => {
+  const color = rule.replace(/\d|bag(s?.?)?/g, '').trim();
+  return !color.includes('no other') ? color : '';
+};
+
+export const part2 = (input: string) => {
+  const bags = parseBags(input);
+  const bagsToCount = ['shiny gold'];
+  let sum = 0;
+
+  while (bagsToCount.length > 0) {
+    const bag = bagsToCount.pop()!;
+    const bagsCounter = bags[bag].reduce((a, rule) => {
+      const amount = parseAmount(rule);
+
+      bagsToCount.push(
+        ...Array(amount)
+          .fill(parseColor(rule))
+          .filter(a => a) // remove '' (no other bags)
+      );
+
+      return a + amount;
+    }, 0);
+
+    sum += bagsCounter;
+  }
+
+  return sum;
+};

src/2020/day7/test.spec.ts

@@ -1,11 +1,16 @@
-import {part1} from './part1';
 import {readInput} from '../../utils';
 
+import {part1} from './part1';
+import {part2} from './part2';
+
 describe('Advent of Code 2020 - Day 7', () => {
   let testInput: string;
+  let testInput2: string;
   let input: string;
+
   beforeAll(async () => {
     testInput = await readInput(__dirname + '/test_input');
+    testInput2 = await readInput(__dirname + '/test_input_2');
     input = await readInput(__dirname + '/input');
   });
 
@@ -18,4 +23,18 @@ describe('Advent of Code 2020 - Day 7', () => {
       expect(part1(input)).toBe(289);
     });
   });
+
+  describe('part 2', () => {
+    it('should output 32 from test_input', () => {
+      expect(part2(testInput)).toBe(32);
+    });
+
+    it('should output 126 from test_input2', () => {
+      expect(part2(testInput2)).toBe(126);
+    });
+
+    it('should output 30055 valid bags from input', () => {
+      expect(part2(input)).toBe(30055);
+    });
+  });
 });

src/2020/day7/test_input_2

@@ -0,0 +1,7 @@
+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.