day 3 part 1

- consider EOF after digit
 - use position and length of numbers to avoid double counting

day03.go

@@ -12,11 +12,17 @@ func isdigit(b byte) bool {
 	return b >= 48 && b <= 57
 }
 
-func engineparts(buf *bufio.Reader) []int {
-	parts := make([]int, 0, 150)
+type enginepart struct {
+	value int
+	pos   int
+	raw   string
+}
+
+func engineparts(buf *bufio.Reader) []enginepart {
+	parts := make([]enginepart, 0, 150)
 
 outer:
-	for {
+	for pos := 0; ; pos++ {
 		head, err := buf.ReadByte()
 		if err != nil {
 			return parts
@@ -30,10 +36,15 @@ outer:
 			// continue reading until number is exhausted
 			for {
 				digit, err := buf.ReadByte()
-				if !isdigit(digit) || err == io.EOF {
+				if !isdigit(digit) {
 					value, _ := strconv.Atoi(string(b))
 					for range b {
-						parts = append(parts, value)
+						parts = append(parts, enginepart{value: value, pos: pos, raw: string(b)})
+					}
+					pos += len(b) - 1
+
+					if err == io.EOF {
+						return parts
 					}
 
 					buf.UnreadByte()
@@ -45,11 +56,11 @@ outer:
 
 		} else if head != '.' {
 			// head is a symbol
-			parts = append(parts, -1)
+			parts = append(parts, enginepart{value: -1, pos: pos, raw: string(head)})
 
 		} else {
 			// head is a '.'
-			parts = append(parts, 0)
+			parts = append(parts, enginepart{value: 0, pos: pos, raw: string(head)})
 		}
 	}
 }
@@ -58,7 +69,7 @@ type day03 struct{}
 
 func (d day03) solve1(r io.Reader) string {
 	sum := 0
-	parts := make([][]int, 0, 100)
+	parts := make([][]enginepart, 0, 100)
 	scanner := bufio.NewScanner(r)
 
 	for scanner.Scan() {
@@ -68,18 +79,25 @@ func (d day03) solve1(r io.Reader) string {
 		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
+	for row := range parts {
+		for item := range parts[row] {
+			if sym := parts[row][item]; sym.value == -1 {
+
+				for i := -1; i < 2; i++ {
+					for j := -1; j < 2; {
+						x := row + i
+						y := item + j
+
+						if x >= 0 && y >= 0 && x < len(parts) && y < len(parts[row]) {
+							part := parts[x][y]
+							if part.value > 0 {
+								sum += part.value
+								j += (part.pos + len(part.raw) - y)
+							} else {
+								j++
+							}
 						}
+
 					}
 				}
 			}