ugly and slow, but it works

03/main.go

@@ -33,18 +33,176 @@ func makeScanner(test bool) *bufio.Scanner {
 	return bufio.NewScanner(reader)
 }
 
+type schematic map[string]entry
+
+type entry struct {
+	num  string
+	symb string
+}
+
+func key(row, col int) string {
+	return fmt.Sprintf("%d.%d", row, col)
+}
+
+func isSymbol(s schematic, row, col int) bool {
+	if c, ok := s[key(row, col)]; ok {
+		return c.symb != ""
+	}
+	return false
+}
+
 func partOne() {
 	scanner := makeScanner(false)
 
+	row := 0
+	schematic := schematic{}
+	// read the whole thing in
 	for scanner.Scan() {
-		// line := scanner.Text()
+		line := scanner.Text()
+		i := struct {
+			tmp []rune
+			col int
+		}{}
+		for col, c := range line {
+			switch c {
+			case '.':
+				if len(i.tmp) != 0 {
+					schematic[key(row, i.col)] = entry{num: string(i.tmp)}
+					i.tmp = []rune{}
 				}
+				continue
+			case '1', '2', '3', '4', '5', '6', '7', '8', '9', '0':
+				if len(i.tmp) == 0 {
+					i.tmp = append(i.tmp, c)
+					i.col = col
+				} else {
+					i.tmp = append(i.tmp, c)
+				}
+				continue
+			default:
+				if len(i.tmp) != 0 {
+					schematic[key(row, i.col)] = entry{num: string(i.tmp)}
+					i.tmp = []rune{}
+				}
+				schematic[key(row, col)] = entry{symb: string(c)}
+				continue
+			}
+		}
+		// check if we have a number still to save but ran out of line
+		if len(i.tmp) != 0 {
+			schematic[key(row, i.col)] = entry{num: string(i.tmp)}
+			i.tmp = []rune{}
+		}
+		row++
+	}
+	sum := 0
+	// now, map back over the schematics and find the parts
+	for row := 0; row <= 139; row++ {
+		for col := 0; col <= 139; col++ {
+			if num, ok := schematic[key(row, col)]; ok && num.num != "" {
+				part := mustAtoi(num.num)
+				if isSymbol(schematic, row, col-1) {
+					// look behind
+					sum += part
+				} else if isSymbol(schematic, row, col+len(num.num)) {
+					// look ahead
+					sum += part
+				} else {
+					for i := -1; i < len(num.num)+1; i++ {
+						// check row above and below
+						if isSymbol(schematic, row-1, col+i) {
+							sum += part
+							break
+						} else if isSymbol(schematic, row+1, col+i) {
+							sum += part
+							break
+						}
+					}
+				}
+			}
+		}
+	}
+	fmt.Println(sum)
 }
 
 func partTwo() {
 	scanner := makeScanner(false)
 
+	row := 0
+	schematic := schematic{}
+	// read the whole thing in
 	for scanner.Scan() {
-		// line := scanner.Text()
+		line := scanner.Text()
+		i := struct {
+			tmp []rune
+			col int
+		}{}
+		for col, c := range line {
+			switch c {
+			case '1', '2', '3', '4', '5', '6', '7', '8', '9', '0':
+				if len(i.tmp) == 0 {
+					i.tmp = append(i.tmp, c)
+					i.col = col
+				} else {
+					i.tmp = append(i.tmp, c)
+				}
+				continue
+			default:
+				if len(i.tmp) != 0 {
+					schematic[key(row, i.col)] = entry{num: string(i.tmp)}
+					i.tmp = []rune{}
+				}
+				if c == '*' { // no longer care about other symbols
+					schematic[key(row, col)] = entry{symb: string(c)}
+				}
+				continue
 			}
 		}
+		// check if we have a number still to save but ran out of line
+		if len(i.tmp) != 0 {
+			schematic[key(row, i.col)] = entry{num: string(i.tmp)}
+			i.tmp = []rune{}
+		}
+		row++
+	}
+	gears := map[string][]int{}
+	// map back over the schematics and find the gears
+	for row := 0; row <= 139; row++ {
+		for col := 0; col <= 139; col++ {
+			if num, ok := schematic[key(row, col)]; ok && num.num != "" {
+				part := mustAtoi(num.num)
+				if isSymbol(schematic, row, col-1) {
+					if schematic[key(row, col-1)].symb == "*" {
+						gears[key(row, col-1)] = append(gears[key(row, col-1)], part)
+					}
+				} else if isSymbol(schematic, row, col+len(num.num)) {
+					if schematic[key(row, col+len(num.num))].symb == "*" {
+						gears[key(row, col+len(num.num))] = append(gears[key(row, col+len(num.num))], part)
+					}
+				} else {
+					for i := -1; i < len(num.num)+1; i++ {
+						// check row above and below
+						if isSymbol(schematic, row-1, col+i) {
+							if schematic[key(row-1, col+i)].symb == "*" {
+								gears[key(row-1, col+i)] = append(gears[key(row-1, col+i)], part)
+							}
+							break
+						} else if isSymbol(schematic, row+1, col+i) {
+							if schematic[key(row+1, col+i)].symb == "*" {
+								gears[key(row+1, col+i)] = append(gears[key(row+1, col+i)], part)
+							}
+							break
+						}
+					}
+				}
+			}
+		}
+	}
+	sum := 0
+	for _, g := range gears {
+		if len(g) == 2 {
+			sum += g[0] * g[1]
+		}
+	}
+	fmt.Println(sum)
+}