Add 2020 day 7

2020/day7/day7.js

@@ -0,0 +1,43 @@
+#!/bin/node
+
+const fs = require('fs');
+
+fs.readFile('input.txt', (err, data) => {
+    const rules = data.toString()
+        .split('\n')
+        .filter(rule => rule.length > 0)
+        .map(rule => rule.split(" bags contain "))
+        .map(rule => [rule[0], rule[1].split(', ')
+            .filter(line => !line.endsWith('no other bags.'))
+            .map(line => line.replace(/ bags?\.?/, ''))
+            .map(line => {
+                const firstSpaceIndex = line.indexOf(' ');
+                return {
+                    count: parseInt(line.substring(0, firstSpaceIndex)),
+                    bagColor: line.substring(firstSpaceIndex + 1),
+                };
+            })]);
+    const ruleMap = {};
+    for (const [containerColor, contents] of rules) {
+        ruleMap[containerColor] = contents;
+    }
+
+    const matchingColors = [];
+    let matchingColorsCount;
+    do {
+        matchingColorsCount = matchingColors.length;
+        for (const [containerColor, contents] of rules) {
+            if (matchingColors.indexOf(containerColor) < 0 &&
+                (contents.find(content => content.bagColor === 'shiny gold' || matchingColors.indexOf(content.bagColor) >= 0))) {
+                matchingColors.push(containerColor);
+            }
+        }
+    } while (matchingColorsCount !== matchingColors.length);
+
+    function countBagsInBag(bagColor, bagCount) {
+        const contents = ruleMap[bagColor];
+        return bagCount + bagCount * contents.reduce((sum, content) => sum + countBagsInBag(content.bagColor, content.count), 0);
+    }
+
+    console.log(matchingColors.length, countBagsInBag('shiny gold', 1) - 1);
+});