d14

d14/d14_test.go

@@ -0,0 +1,53 @@
+package d14
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestP1(t *testing.T) {
+	result := P1(`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`)
+
+	assert.EqualValues(t, 1588, result)
+}
+
+func TestP2(t *testing.T) {
+	result := P2(`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`)
+
+	assert.EqualValues(t, 2188189693529, result)
+}

d14/p1.go

@@ -0,0 +1,68 @@
+package d14
+
+import (
+	"strings"
+
+	"golang.org/x/exp/maps"
+	"golang.org/x/exp/slices"
+)
+
+func reduce[S any, A any](slice []S, f func(elm S, acc A) A, acc A) A {
+	for _, elm := range slice {
+		acc = f(elm, acc)
+	}
+	return acc
+}
+
+func makePairs(template string) map[string]int {
+	pairs := make(map[string]int)
+
+	for i := 0; i < len(template)-1; i++ {
+		pairs[string(template[i])+string(template[i+1])] = 1
+	}
+
+	return pairs
+}
+
+func templateAndInstructions(in string) (string, map[string]string) {
+	parts := strings.Split(strings.TrimSpace(in), "\n\n")
+	instructions := make(map[string]string)
+	for _, pair := range strings.Split(parts[1], "\n") {
+		mapping := strings.Split(pair, " -> ")
+		instructions[mapping[0]] = mapping[1]
+	}
+	return parts[0], instructions
+}
+
+func count(template string, instructions map[string]string, runs int) map[string]int {
+	init := func(char string, acc map[string]int) map[string]int { acc[char]++; return acc }
+	counts := reduce(strings.Split(template, ""), init, make(map[string]int))
+	pairs := makePairs(template)
+	for i := 0; i < runs; i++ {
+		for pair, count := range maps.Clone(pairs) {
+			left := pair[:1]
+			right := pair[1:]
+			middle := instructions[pair]
+			pairs[pair] -= count
+			pairs[left+middle] += count
+			pairs[middle+right] += count
+			counts[middle] += count
+		}
+	}
+
+	return counts
+}
+
+func countPolymer(in string, runs int) int {
+	template, instructions := templateAndInstructions(in)
+	counts := maps.Values(count(template, instructions, runs))
+	slices.Sort(counts)
+	max := counts[len(counts)-1]
+	min := counts[0]
+
+	return max - min
+}
+
+func P1(in string) int {
+	return countPolymer(in, 10)
+}

d14/p2.go

@@ -0,0 +1,5 @@
+package d14
+
+func P2(in string) int {
+	return countPolymer(in, 40)
+}

go.mod

@@ -1,10 +1,12 @@
 module github.com/fotonmoton/aoc2021
 
-go 1.17
+go 1.18
+
+require github.com/stretchr/testify v1.7.0
 
 require (
 	github.com/davecgh/go-spew v1.1.0 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
-	github.com/stretchr/testify v1.7.0 // indirect
+	golang.org/x/exp v0.0.0-20220428152302-39d4317da171 // indirect
 	gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c // indirect
 )

go.sum

@@ -5,6 +5,9 @@ github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZN
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+golang.org/x/exp v0.0.0-20220428152302-39d4317da171 h1:TfdoLivD44QwvssI9Sv1xwa5DcL5XQr4au4sZ2F2NV4=
+golang.org/x/exp v0.0.0-20220428152302-39d4317da171/go.mod h1:lgLbSvA5ygNOMpwM/9anMpWVlVJ7Z+cHWq/eFuinpGE=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

main.go

@@ -12,6 +12,7 @@ import (
 	"github.com/fotonmoton/aoc2021/d11"
 	"github.com/fotonmoton/aoc2021/d12"
 	"github.com/fotonmoton/aoc2021/d13"
+	"github.com/fotonmoton/aoc2021/d14"
 	"github.com/fotonmoton/aoc2021/d2"
 	"github.com/fotonmoton/aoc2021/d3"
 	"github.com/fotonmoton/aoc2021/d4"
@@ -58,4 +59,6 @@ func main() {
 	fmt.Printf("day 12 part 2: %v\n", d12.P2(client.Day(12)))
 	fmt.Printf("day 13: %v\n", d13.P1(client.Day(13)))
 	fmt.Printf("day 13 part 2: %v\n", d13.P2(client.Day(13)))
+	fmt.Printf("day 14: %v\n", d14.P1(client.Day(14)))
+	fmt.Printf("day 14 part 2: %v\n", d14.P2(client.Day(14)))
 }