add day-07 + benchmarks

day-07/internal/two/benchmark

@@ -0,0 +1,6 @@
+goos: linux
+goarch: amd64
+pkg: github.com/onyx-and-iris/aoc2024/day-07/internal/two
+cpu: Intel(R) Core(TM) i7-8700K CPU @ 3.70GHz
+BenchmarkSolve-12    	1000000000	         0.2539 ns/op
+ok  	github.com/onyx-and-iris/aoc2024/day-07/internal/two	3.822s

day-07/internal/two/equation.go

@@ -0,0 +1,10 @@
+package two
+
+type equation struct {
+	target   int
+	operands []int
+}
+
+func newEquation(res int, operands []int) equation {
+	return equation{res, operands}
+}

day-07/internal/two/op.go

@@ -0,0 +1,7 @@
+package two
+
+const (
+	sumOp  = "+"
+	prodOp = "*"
+	joinOp = "||"
+)

day-07/internal/two/solve.go

@@ -0,0 +1,70 @@
+package two
+
+import (
+	"bytes"
+	"fmt"
+
+	log "github.com/sirupsen/logrus"
+)
+
+func Solve(buf []byte) (int, error) {
+	r := bytes.NewReader(buf)
+	equations, err := parseLines(r)
+	if err != nil {
+		return 0, err
+	}
+
+	conc := len(equations)
+	sumChan := make(chan int)
+
+	for _, equation := range equations {
+		go func() {
+			var total int
+			if res, ok := next(equation.target, equation.operands, total, joinOp); ok {
+				sumChan <- res
+				return
+			}
+			sumChan <- 0
+		}()
+	}
+
+	var sum int
+	for range conc {
+		res := <-sumChan
+		sum += res
+	}
+
+	return sum, nil
+}
+
+func next(target int, operands []int, total int, operator string) (int, bool) {
+	if len(operands) == 0 {
+		if total == target {
+			log.Debug(total)
+			return total, true
+		}
+		return 0, false
+	}
+
+	switch operator {
+	case sumOp:
+		total += operands[0]
+	case prodOp:
+		total *= operands[0]
+	case joinOp:
+		opStr := fmt.Sprintf("%d%d", total, operands[0])
+		total = mustConv(opStr)
+	}
+
+	if res, ok := next(target, operands[1:], total, sumOp); ok {
+		return res, ok
+	}
+	if res, ok := next(target, operands[1:], total, prodOp); ok {
+		return res, ok
+	}
+	if res, ok := next(target, operands[1:], total, joinOp); ok {
+		return res, ok
+	}
+
+	return 0, false
+}

day-07/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-07/internal/two/util.go

@@ -0,0 +1,37 @@
+package two
+
+import (
+	"bufio"
+	"io"
+	"strconv"
+	"strings"
+)
+
+func mustConv(s string) int {
+	n, err := strconv.Atoi(s)
+	if err != nil {
+		panic(err)
+	}
+	return n
+}
+
+func parseLines(r io.Reader) ([]equation, error) {
+	equations := []equation{}
+
+	scanner := bufio.NewScanner(r)
+	for scanner.Scan() {
+		parts := strings.Split(scanner.Text(), ":")
+		res := mustConv(parts[0])
+		var operands []int
+		for _, s := range strings.Fields(parts[1]) {
+			operands = append(operands, mustConv(string(s)))
+		}
+		equations = append(equations, newEquation(res, operands))
+	}
+
+	if err := scanner.Err(); err != nil {
+		return nil, err
+	}
+
+	return equations, nil
+}