Solution for day 14 (2021)

Author: joshthompson

2021/14/index.js

@@ -0,0 +1,45 @@
+const fs = require('fs')
+
+const start = +new Date()
+fs.readFile(`${__dirname}/input.txt`, (_e, data) => {
+  const { polymerTemplate, pairInsertionRules } = processInput(data.toString())
+  console.log('Part 1', run(polymerTemplate, pairInsertionRules, 10))
+  console.log('Part 2', run(polymerTemplate, pairInsertionRules, 40))
+  console.log('Time:', new Date() - start, 'ms')
+})
+
+function processInput(input) {
+  const [polymerTemplate, rulesInput] = input.split('\n\n')
+  const pairInsertionRules = new Map(rulesInput.split('\n').map(rule => rule.split(' -> ')))
+  return { polymerTemplate, pairInsertionRules }
+}
+
+function run(polymerTemplate, pairInsertionRules, iterations) {
+  const pairs = {}
+  const chars = {}
+  for (let p = 0; p < polymerTemplate.length; p++) {
+    chars[polymerTemplate[p]] = (chars[polymerTemplate[p]] || 0) + 1
+    if (polymerTemplate[p + 1]) {
+      const pair = polymerTemplate[p] + polymerTemplate[p + 1]
+      pairs[pair] = (pairs[pair] || 0) + 1
+    }
+  }
+  for (let i = 0; i < iterations; i++) {
+    const currentPairs = Object.entries(pairs)
+    for (let p in pairs) {
+      pairs[p] = 0
+    }
+    currentPairs.forEach(([pair, tally]) => {
+      const rule = pairInsertionRules.get(pair)
+      if (rule) {
+        const pair1 = pair[0] + rule
+        const pair2 = rule + pair[1]
+        chars[rule] = (chars[rule] || 0) + tally
+        pairs[pair1] = (pairs[pair1] || 0) + tally
+        pairs[pair2] = (pairs[pair2] || 0) + tally
+      }
+    })
+  }
+  const values = Object.values(chars).sort((a, b) => a - b)
+  return values[values.length - 1] - values[0]
+}

2021/14/input.txt

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+SCSCSKKVVBKVFKSCCSOV
+
+CP -> C
+SF -> S
+BH -> F
+SS -> N
+KB -> N
+NO -> N
+BP -> F
+NK -> P
+VP -> H
+OF -> O
+VH -> O
+FV -> F
+OP -> V
+FP -> B
+VB -> B
+OK -> S
+BS -> B
+SK -> P
+VV -> H
+PC -> S
+HV -> K
+PS -> N
+VS -> O
+HF -> B
+SV -> C
+HP -> O
+NF -> V
+HB -> F
+VO -> B
+VN -> N
+ON -> H
+KV -> K
+OV -> F
+HO -> H
+NB -> K
+CB -> F
+FF -> H
+NH -> F
+SN -> N
+PO -> O
+PH -> C
+HH -> P
+KF -> N
+OH -> N
+KS -> O
+FH -> H
+CC -> F
+CK -> N
+FC -> F
+CF -> H
+HN -> B
+OC -> F
+OB -> K
+FO -> P
+KP -> N
+NC -> P
+PN -> O
+PV -> B
+CO -> C
+CS -> P
+PP -> V
+FN -> B
+PK -> C
+VK -> S
+HS -> P
+OS -> N
+NP -> K
+SB -> F
+OO -> F
+CV -> V
+BB -> O
+SH -> O
+NV -> N
+BN -> C
+KN -> H
+KC -> C
+BK -> O
+KO -> S
+VC -> N
+KK -> P
+BO -> V
+BC -> V
+BV -> H
+SC -> N
+NN -> C
+CH -> H
+SO -> P
+HC -> F
+FS -> P
+VF -> S
+BF -> S
+PF -> O
+SP -> H
+FK -> N
+NS -> C
+PB -> S
+HK -> C
+CN -> B
+FB -> O
+KH -> O

2021/14/test.txt

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+NNCB
+
+CH -> B
+HH -> N
+CB -> H
+NH -> C
+HB -> C
+HC -> B
+HN -> C
+NN -> C
+BH -> H
+NC -> B
+NB -> B
+BN -> B
+BB -> N
+BC -> B
+CC -> N
+CN -> C