solve day 1 part 1

day01.go

@@ -0,0 +1,68 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"strconv"
+	"unicode"
+)
+
+type day01 struct {
+}
+
+type buffer struct {
+	first bool
+	d1    rune
+
+	last bool
+	d2   rune
+}
+
+func (b *buffer) value() (value uint64) {
+	var d2 rune
+
+	if b.last {
+		d2 = b.d2
+	} else {
+		d2 = b.d1
+	}
+
+	str := fmt.Sprintf("%c%c", b.d1, d2)
+	value, _ = strconv.ParseUint(str, 10, 64)
+
+	b.first, b.last = false, false
+	return
+}
+
+func (b *buffer) record(digit rune) {
+	if !b.first {
+		b.d1 = digit
+		b.first = true
+	} else {
+		b.d2 = digit
+		b.last = true
+	}
+}
+
+func (d day01) solve(r io.Reader) string {
+	var (
+		buffer buffer
+		total  uint64
+		buf    = bufio.NewReader(r)
+	)
+
+	for {
+		b, _, err := buf.ReadRune()
+		if err != nil {
+			return fmt.Sprintf("%d", total+buffer.value())
+		}
+
+		if unicode.IsDigit(b) {
+			buffer.record(b)
+		} else if b == '\n' {
+			total += buffer.value()
+		}
+
+	}
+}

main.go

@@ -0,0 +1,68 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"path/filepath"
+	"strconv"
+)
+
+type puzzle interface {
+	solve(r io.Reader) string
+}
+
+var (
+	// pick which day to run with a flag
+	day = flag.String("d", "", "which day to solve")
+
+	// slice of all puzzles
+	puzzles = []puzzle{
+		&day01{},
+	}
+)
+
+func init() {
+	flag.Parse()
+
+}
+
+func inputs(day int64) []io.Reader {
+	inputs := make([]io.Reader, 0, 2)
+	path := fmt.Sprintf("input/%d-[1-2]", day)
+
+	matches, err := filepath.Glob(path)
+	if err != nil {
+		log.Fatalf("matching puzzle input files: %s", err.Error())
+	}
+
+	fmt.Println(matches)
+
+	for _, match := range matches {
+		f, err := os.Open(match)
+		if err == nil {
+			inputs = append(inputs, f)
+		}
+	}
+
+	return inputs
+}
+
+func main() {
+	puzzleIndex, err := strconv.ParseInt(*day, 10, 32)
+	if err != nil {
+		log.Fatalf("invalid puzzle day: %s", *day)
+	}
+	inputs := inputs(puzzleIndex)
+
+	puzzle := puzzles[puzzleIndex-1]
+
+	fmt.Fprintf(os.Stdout, "Day %d:\n", puzzleIndex)
+	for i := range inputs {
+		ans := puzzle.solve(inputs[i])
+		fmt.Fprintf(os.Stdout, "Solution %d:\n%s", i+1, ans)
+	}
+	fmt.Fprintln(os.Stdout)
+}