attempt day 3

day03.go

@@ -0,0 +1,94 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"strconv"
+	"strings"
+)
+
+func isdigit(b byte) bool {
+	return b >= 48 && b <= 57
+}
+
+func engineparts(buf *bufio.Reader) []int {
+	parts := make([]int, 0, 150)
+
+outer:
+	for {
+		head, err := buf.ReadByte()
+		if err != nil {
+			return parts
+		}
+
+		if isdigit(head) {
+			// start recording digits
+			b := make([]byte, 0, 10)
+			b = append(b, head)
+
+			// continue reading until number is exhausted
+			for {
+				digit, err := buf.ReadByte()
+				if !isdigit(digit) || err == io.EOF {
+					value, _ := strconv.Atoi(string(b))
+					for range b {
+						parts = append(parts, value)
+					}
+
+					buf.UnreadByte()
+					continue outer
+				}
+
+				b = append(b, digit)
+			}
+
+		} else if head != '.' {
+			// head is a symbol
+			parts = append(parts, -1)
+
+		} else {
+			// head is a '.'
+			parts = append(parts, 0)
+		}
+	}
+}
+
+type day03 struct{}
+
+func (d day03) solve1(r io.Reader) string {
+	sum := 0
+	parts := make([][]int, 0, 100)
+	scanner := bufio.NewScanner(r)
+
+	for scanner.Scan() {
+		line := scanner.Text()
+		buf := bufio.NewReader(strings.NewReader(line))
+		lineparts := engineparts(buf)
+		parts = append(parts, lineparts)
+	}
+
+	for i := 1; i < len(parts)-1; i++ {
+		for j := 1; j < len(parts[i])-1; j++ {
+			cursor := parts[i][j]
+			if cursor == -1 {
+			row:
+				for i2 := -1; i2 <= 1; i2++ {
+					for j2 := -1; j2 <= 1; j2++ {
+						val := parts[i+i2][j+j2]
+						if val > 0 {
+							sum += val
+							continue row
+						}
+					}
+				}
+			}
+		}
+	}
+
+	return fmt.Sprintf("%d", sum)
+}
+
+func (d day03) solve2(r io.Reader) string {
+	return ""
+}

main.go

@@ -22,6 +22,7 @@ var (
 	puzzles = []puzzle{
 		&day01{},
 		&day02{},
+		&day03{},
 	}
 )
 

main_test.go

@@ -60,3 +60,24 @@ Game 5: 6 red, 1 blue, 3 green; 2 blue, 1 red, 2 green`
 	}
 
 }
+
+func TestDay03(t *testing.T) {
+	input1 := `467..114..
+...*......
+..35..633.
+......#...
+617*......
+.....+.58.
+..592.....
+......755.
+...$.*....
+.664.598..`
+
+	puzzle := day03{}
+
+	ans1 := "4361"
+	res1 := puzzle.solve1(strings.NewReader(input1))
+	if res1 != ans1 {
+		t.Errorf("day 3 solution 1 = %s; wanted %s", res1, ans1)
+	}
+}