Feat/2020 day 07

2020/day-07/bagRules.js

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+const console = require('../helpers')
+
+const parseRule = (rule) => {
+  const result = {}
+  // Get the color of the outer bag
+  const outRemainder = rule.split(' contain ')
+  result.outer = outRemainder.shift().replace('bags', 'bag')
+  // Get the color and values of inner bags
+  if (outRemainder[0] !== 'no other bags.') {
+    result.inner = outRemainder[0].split(', ').map((str) => {
+      const inRemainder = str.split(' ')
+      const count = Number(inRemainder.shift())
+      const color = inRemainder.join(' ')
+        .replace('.', '')
+        .replace('bags', 'bag')
+      return {
+        count,
+        color
+      }
+    })
+  }
+
+  return result
+}
+
+const findAllowedOuter = (rules, color) => {
+  const isAllowed = (rule) => {
+    if (!rule.inner) return false
+    return (
+      rule.inner.filter((child) => {
+        return (
+          child.color === color
+        )
+      }).length > 0
+    )
+  }
+
+  const allowed = {}
+
+  // Loop through the rules, find all colors this bag is allowed within
+  rules.filter(isAllowed).forEach((rule) => {
+    allowed[rule.outer] = true
+  })
+
+  // Take the list of allowed colors, and find out which they are allowed within
+  Object.keys(allowed).forEach((color) => {
+    const temp = findAllowedOuter(rules, color)
+    if (Object.keys(temp).length > 0) {
+      Object.assign(allowed, temp)
+    }
+  })
+
+  return allowed
+}
+
+const countInner = (rules, color, count = 1) => {
+  // const children = {}
+  /** checks if rule matches color */
+  const matchesColor = ({ outer }) => outer === color
+  /** checks if rule has child bags */
+  const hasChildren = ({ inner }) => (inner) && inner.length > 0
+
+  const getChildrenBags = ({ inner }, multiplier = 1) => {
+    const res = {}
+    // Convert into structured list
+    inner.forEach(({ color, count }) => {
+      res[color] = count * multiplier
+    })
+    return res
+  }
+  /** type-safe addition */
+  const add = (a, b) => {
+    a = (typeof a === 'number') ? a : 0
+    b = (typeof b === 'number') ? b : 0
+    return a + b
+  }
+  /** combine two objects using the specified operator method for collsions */
+  const combineObjects = (a = {}, b = {}, operator) => {
+    const c = {}
+    // check for collisions between fields across the objects and run operator() on them
+    for (const [key, value] of Object.entries(b)) {
+      c[key] = operator(a[key], value)
+    }
+    return Object.assign({}, a, c) // b not needed because covered in collision resolver
+  }
+
+  console.debug('matching', color)
+
+  // Loop through the rules to find first level children
+  return rules
+    .filter(matchesColor) // find all matches for the color
+    .filter(hasChildren) // filter for matches that have children
+    .map(rule => getChildrenBags(rule, count)) // get the counts from the children
+    .reduce((res, children) => {
+      // Add everything back together
+      const childrensChildren = Object.entries(children)
+        .map(([key, value]) => countInner(rules, key, value))
+        .reduce((r, c) => combineObjects(r, c, add), {})
+
+      res = combineObjects(res, children, add)
+      res = combineObjects(res, childrensChildren, add)
+
+      return res
+    }, {})
+}
+
+module.exports = {
+  parseRule,
+  findAllowedOuter,
+  countInner
+}

2020/day-07/bagRules.test.js

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+/* eslint-env mocha */
+const { expect } = require('chai')
+const { parseRule, findAllowedOuter, countInner } = require('./bagRules')
+
+const testData = {
+  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.'
+  ],
+  part2Rules: [
+    '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.'
+  ]
+}
+
+describe('--- Day 7: Handy Haversacks ---', () => {
+  describe('Part 1', () => {
+    describe('parseRule()', () => {
+      it('converts a natural language rule into a useable object', () => {
+        expect(parseRule(testData.rules[0])).to.deep.equal({
+          outer: 'light red bag',
+          inner: [
+            {
+              count: 1,
+              color: 'bright white bag'
+            }, {
+              count: 2,
+              color: 'muted yellow bag'
+            }
+          ]
+        })
+      })
+      it('handles bags that do not accept children', () => {
+        expect(parseRule(testData.rules[7])).to.deep.equal({
+          outer: 'faded blue bag'
+        })
+      })
+    })
+    describe('findAllowedOuter()', () => {
+      it('list bags the specified bag is allowed to be placed in', () => {
+        const expectedColors = [
+          'bright white bag',
+          'muted yellow bag',
+          'dark orange bag',
+          'light red bag'
+        ]
+        const result = findAllowedOuter(
+          testData.rules.map(parseRule),
+          'shiny gold bag'
+        )
+        expectedColors.forEach(color => {
+          expect(result[color]).to.equal(true)
+        })
+        expect(Object.keys(result).length).to.equal(expectedColors.length)
+      })
+    })
+  })
+  describe('Part 2', () => {
+    describe('countInner()', () => {
+      it('provides a list of child bags and with quantity of each', () => {
+        const result1 = Object.values(
+          countInner(testData.rules.map(parseRule), 'shiny gold bag')
+        ).reduce((a, b) => a + b, 0)
+        expect(result1).to.equal(32)
+
+        const result2 = Object.values(
+          countInner(testData.part2Rules.map(parseRule), 'shiny gold bag')
+        ).reduce((a, b) => a + b, 0)
+        expect(result2).to.equal(126)
+      })
+    })
+  })
+})

2020/day-07/index.js

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+// eslint-disable-next-line no-unused-vars
+const console = require('../helpers')
+require('./solution')