Day 14

14/input.txt

@@ -0,0 +1,102 @@
+FNFPPNKPPHSOKFFHOFOC
+
+VS -> B
+SV -> C
+PP -> N
+NS -> N
+BC -> N
+PB -> F
+BK -> P
+NV -> V
+KF -> C
+KS -> C
+PV -> N
+NF -> S
+PK -> F
+SC -> F
+KN -> K
+PN -> K
+OH -> F
+PS -> P
+FN -> O
+OP -> B
+FO -> C
+HS -> F
+VO -> C
+OS -> B
+PF -> V
+SB -> V
+KO -> O
+SK -> N
+KB -> F
+KH -> C
+CC -> B
+CS -> C
+OF -> C
+FS -> B
+FP -> H
+VN -> O
+NB -> N
+BS -> H
+PC -> H
+OO -> F
+BF -> O
+HC -> P
+BH -> S
+NP -> P
+FB -> C
+CB -> H
+BO -> C
+NN -> V
+SF -> N
+FC -> F
+KK -> C
+CN -> N
+BV -> F
+FK -> C
+CF -> F
+VV -> B
+VF -> S
+CK -> C
+OV -> P
+NC -> N
+SS -> F
+NK -> V
+HN -> O
+ON -> P
+FH -> O
+OB -> H
+SH -> H
+NH -> V
+FF -> B
+HP -> B
+PO -> P
+HB -> H
+CH -> N
+SN -> P
+HK -> P
+FV -> H
+SO -> O
+VH -> V
+BP -> V
+CV -> P
+KP -> K
+VB -> N
+HV -> K
+SP -> N
+HO -> P
+CP -> H
+VC -> N
+CO -> S
+BN -> H
+NO -> B
+HF -> O
+VP -> K
+KV -> H
+KC -> F
+HH -> C
+BB -> K
+VK -> P
+OK -> C
+OC -> C
+PH -> H

14/main.go

@@ -0,0 +1,72 @@
+package main
+
+import (
+	"log"
+	"math"
+	"os"
+	"strings"
+)
+
+func main() {
+	inputBytes, _ := os.ReadFile("input.txt")
+	input := strings.Split(string(inputBytes), "\n")
+
+	log.Println("Puzzle 1:", puzzle1(input))
+	log.Println("Puzzle 2:", puzzle2(input))
+}
+
+func puzzle1(input []string) int {
+	return do(input, 10)
+}
+
+func puzzle2(input []string) int {
+	return do(input, 40)
+}
+
+func parseInput(input []string) (template string, rules map[string]string) {
+	template = input[0]
+	rules = map[string]string{}
+	for _, line := range input[2:] {
+		parts := strings.Split(line, " -> ")
+		rules[parts[0]] = parts[1]
+	}
+	return
+}
+
+func do(input []string, steps int) int {
+	// Parse input
+	template, rules := parseInput(input)
+	// Polymerize
+	pairs := map[string]int{}
+	for i := 0; i < len(template)-1; i++ {
+		pairs[template[i:i+2]]++
+	}
+	for i := 0; i < steps; i++ {
+		newPairs := map[string]int{}
+		for pair, count := range pairs {
+			rule := rules[pair]
+			newPairs[pair[0:1]+rule] += count
+			newPairs[rule+pair[1:2]] += count
+		}
+		pairs = newPairs
+	}
+	// Sum up counts for each letter
+	counts := map[byte]int{}
+	for pair, count := range pairs {
+		counts[pair[0]] += count
+	}
+	// Add count for last letter in template
+	counts[template[len(template)-1]]++
+	// Get minimum and maximum counts
+	max, min := math.MinInt, math.MaxInt
+	for _, count := range counts {
+		if count > max {
+			max = count
+		}
+		if count < min {
+			min = count
+		}
+	}
+	// Return difference
+	return max - min
+}

14/main_test.go

@@ -0,0 +1,17 @@
+package main
+
+import (
+	"os"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test(t *testing.T) {
+	inputBytes, _ := os.ReadFile("test.txt")
+	input := strings.Split(string(inputBytes), "\n")
+
+	assert.Equal(t, 1588, puzzle1(input))
+	assert.Equal(t, 2188189693529, puzzle2(input))
+}

14/test.txt

@@ -0,0 +1,18 @@
+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