2021.14

challenges/2021/14.js

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+// Part 1
+const solvePuzzle1 = (input) => breedElements(input, 10);
+
+// Part 2
+const solvePuzzle2 = (input) => breedElements(input, 40);
+
+const breedElements = (input, steps) => {
+  input = parseInput(input);
+  const [template, ...pairs] = input;
+  const polymerTemplate = template.split("");
+
+  const pairMap = new Map(pairs.map((l) => l.split(" -> ")));
+  const pairCounts = new Map();
+
+  const frequencies = {};
+  polymerTemplate.forEach((x) => (frequencies[x] = (frequencies[x] || 0) + 1));
+
+  for (let j = 0; j < polymerTemplate.length - 1; j++) {
+    const pair = polymerTemplate[j] + polymerTemplate[j + 1];
+    pairCounts.set(pair, (pairCounts.get(pair) || 0) + 1);
+  }
+
+  for (let i = 0; i < steps; i++) {
+    const copyOfPairCounts = new Map(pairCounts);
+    for (let [pair, count] of copyOfPairCounts) {
+      const midChar = pairMap.get(pair);
+      const [leftPair, rightPair] = [pair[0] + midChar, midChar + pair[1]];
+
+      frequencies[midChar] = (frequencies[midChar] || 0) + count;
+
+      pairCounts.set(pair, pairCounts.get(pair) - count);
+      pairCounts.set(leftPair, (pairCounts.get(leftPair) || 0) + count);
+      pairCounts.set(rightPair, (pairCounts.get(rightPair) || 0) + count);
+    }
+  }
+
+  const sortedFrequencies = Array.from(Object.entries(frequencies)).sort(([_, a], [__, b]) => a - b);
+  return sortedFrequencies[sortedFrequencies.length - 1][1] - sortedFrequencies[0][1];
+};
+
+const parseInput = (input) => input.split("\n").filter((x) => x !== "");
+
+require(__dirname + "/../../utils/test.js").test(__filename, __dirname, solvePuzzle1);
+require(__dirname + "/../../utils/test.js").test(__filename, __dirname, solvePuzzle2);

challenges/2021/inputs/14.txt

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