add day-21 + benchmarks

day-21/internal/two/benchmark

@@ -0,0 +1,6 @@
+goos: linux
+goarch: amd64
+pkg: github.com/onyx-and-iris/aoc2024/day-21/internal/two
+cpu: Intel(R) Core(TM) i7-8700K CPU @ 3.70GHz
+BenchmarkSolve-12    	1000000000	         0.0007436 ns/op
+ok  	github.com/onyx-and-iris/aoc2024/day-21/internal/two	0.011s

day-21/internal/two/cache.go

@@ -0,0 +1,41 @@
+package two
+
+import "sync"
+
+type robotCache struct {
+	mu   *sync.RWMutex
+	data map[string]map[int]int
+}
+
+func newRobotCache() robotCache {
+	return robotCache{
+		mu:   &sync.RWMutex{},
+		data: make(map[string]map[int]int),
+	}
+}
+
+func (rc *robotCache) read(moves string, id int) (int, bool) {
+	rc.mu.RLock()
+	defer rc.mu.RUnlock()
+
+	v, ok := rc.data[moves][id]
+	return v, ok
+}
+
+func (rc *robotCache) contains(moves string) bool {
+	rc.mu.RLock()
+	defer rc.mu.RUnlock()
+
+	_, ok := rc.data[moves]
+	return ok
+}
+
+func (rc *robotCache) insert(moves string, id, val int) {
+	rc.mu.Lock()
+	defer rc.mu.Unlock()
+
+	if _, ok := rc.data[moves]; !ok {
+		rc.data[moves] = make(map[int]int)
+	}
+	rc.data[moves][id] = val
+}

day-21/internal/two/solve.go

@@ -0,0 +1,71 @@
+package two
+
+import (
+	"bytes"
+	"strings"
+
+	"github.com/onyx-and-iris/aoc2024/day-21/internal/pad"
+)
+
+func Solve(buf []byte) (int, error) {
+	r := bytes.NewReader(buf)
+	codes, err := parseLines(r)
+	if err != nil {
+		return 0, err
+	}
+
+	complexityChan := make(chan int)
+	conc := len(codes)
+
+	for _, code := range codes {
+		go func() {
+			numpad := pad.NewNumpad()
+			dirpad := pad.NewDirpad()
+			complexityChan <- numFromCode(code) * generateIntFromMoves(numpad, dirpad, code, 25)
+		}()
+	}
+
+	var complexity int
+	for range conc {
+		complexity += <-complexityChan
+	}
+
+	return complexity, nil
+}
+
+type generator interface {
+	Generate(code string) string
+}
+
+func generateIntFromMoves(n, d generator, code string, numRobots int) int {
+	moves := n.Generate(code)
+	return recurseForRobots(d, moves, numRobots, 1, newRobotCache())
+}
+
+func recurseForRobots(
+	d generator,
+	moves string,
+	numRobots int,
+	id int,
+	memo robotCache,
+) int {
+	if memo.contains(moves) {
+		if v, ok := memo.read(moves, id-1); ok {
+			return v
+		}
+	}
+
+	next := d.Generate(moves)
+	if id == numRobots {
+		return len(next)
+	}
+
+	var totalCount int
+	for _, move := range strings.SplitAfter(next, "A") {
+		count := recurseForRobots(d, move, numRobots, id+1, memo)
+		totalCount += count
+	}
+	memo.insert(moves, id-1, totalCount)
+
+	return totalCount
+}

day-21/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-21/internal/two/util.go

@@ -0,0 +1,27 @@
+package two
+
+import (
+	"bufio"
+	"io"
+	"strconv"
+)
+
+func parseLines(r io.Reader) ([]string, error) {
+	codes := []string{}
+
+	scanner := bufio.NewScanner(r)
+	for scanner.Scan() {
+		codes = append(codes, scanner.Text())
+	}
+
+	if err := scanner.Err(); err != nil {
+		return nil, err
+	}
+
+	return codes, nil
+}
+
+func numFromCode(s string) int {
+	n, _ := strconv.Atoi(s[:len(s)-1])
+	return n
+}