add day-22 + benchmarks

day-22/internal/two/benchmark

@@ -0,0 +1,6 @@
+goos: linux
+goarch: amd64
+pkg: github.com/onyx-and-iris/aoc2024/day-22/internal/two
+cpu: Intel(R) Core(TM) i7-8700K CPU @ 3.70GHz
+BenchmarkSolve-12    	       1	2064547562 ns/op
+ok  	github.com/onyx-and-iris/aoc2024/day-22/internal/two	2.091s

day-22/internal/two/cache.go

@@ -0,0 +1,21 @@
+package two
+
+import "sync"
+
+type sequenceCache struct {
+	mu   sync.RWMutex
+	data map[sequence]int
+}
+
+func newSequenceCache() sequenceCache {
+	return sequenceCache{
+		data: make(map[sequence]int),
+	}
+}
+
+func (sc *sequenceCache) upsert(seq sequence, value int) {
+	sc.mu.Lock()
+	defer sc.mu.Unlock()
+
+	sc.data[seq] += value
+}

day-22/internal/two/sequence.go

@@ -0,0 +1,7 @@
+package two
+
+type sequence [4]int
+
+func (s *sequence) shift(next int) {
+	s[0], s[1], s[2], s[3] = s[1], s[2], s[3], next
+}

day-22/internal/two/solve.go

@@ -0,0 +1,56 @@
+package two
+
+import (
+	"bytes"
+	"math"
+
+	"github.com/onyx-and-iris/aoc2024/day-22/internal/randomiser"
+)
+
+const numIterations = 2000
+
+func Solve(buf []byte) (int, error) {
+	r := bytes.NewReader(buf)
+	secrets, err := parseLines(r)
+	if err != nil {
+		return 0, err
+	}
+
+	conc := len(secrets)
+	done := make(chan bool)
+
+	sequences := newSequenceCache()
+	for _, secret := range secrets {
+		go func() {
+			seen := make(map[sequence]struct{})
+			sequence := sequence{math.MaxInt, math.MaxInt, math.MaxInt, math.MaxInt}
+
+			randomiser := randomiser.New(secret)
+			for range numIterations {
+				prev := lastDigit(randomiser.Secret())
+				randomiser.Randomise()
+
+				sequence.shift(prev - lastDigit(randomiser.Secret()))
+
+				_, ok := seen[sequence]
+				if !ok {
+					seen[sequence] = struct{}{}
+					sequences.upsert(sequence, lastDigit(randomiser.Secret()))
+				}
+			}
+			done <- true
+		}()
+	}
+
+	for range conc {
+		<-done
+	}
+
+	max := 0
+	for _, sum := range sequences.data {
+		if sum > max {
+			max = sum
+		}
+	}
+	return max, nil
+}

day-22/internal/two/solve_internal_test.go

@@ -0,0 +1,15 @@
+package two
+
+import (
+	_ "embed"
+	"os"
+	"testing"
+)
+
+//go:embed testdata/input.txt
+var data []byte
+
+func BenchmarkSolve(b *testing.B) {
+	os.Stdout, _ = os.Open(os.DevNull)
+	Solve(data)
+}

day-22/internal/two/util.go

@@ -0,0 +1,35 @@
+package two
+
+import (
+	"bufio"
+	"io"
+	"strconv"
+	"strings"
+)
+
+func parseLines(r io.Reader) ([]int, error) {
+	secrets := []int{}
+
+	scanner := bufio.NewScanner(r)
+	for scanner.Scan() {
+		secrets = append(secrets, mustConv(strings.TrimSpace(scanner.Text())))
+	}
+
+	if err := scanner.Err(); err != nil {
+		return nil, err
+	}
+
+	return secrets, nil
+}
+
+func mustConv(s string) int {
+	n, err := strconv.Atoi(s)
+	if err != nil {
+		panic(err)
+	}
+	return n
+}
+
+func lastDigit(n int) int {
+	return n % 10
+}