1 files changed, 81 insertions(+), 3 deletions(-)

M 2023/03.go

@@ 99,8 99,86 @@ func partA(fn string) {
 	log.Printf("%s: %v", fn, a)
 }
 
+type XY struct {
+	x, y int
+}
+
+func adjacentGears(ls []string, x, y int) []XY {
+	X := len(ls[0])
+	Y := len(ls)
+
+	var xy []XY
+
+	if y > 0 {
+		if x > 0 && ls[y-1][x-1] == '*' {
+			xy = append(xy, XY { x-1, y-1 })
+		}
+
+		if ls[y-1][x] == '*' {
+			xy = append(xy, XY { x, y-1 })
+		}
+
+		if x+1 < X && ls[y-1][x+1] == '*' {
+			xy = append(xy, XY { x+1, y-1 })
+		}
+	}
+
+	if x > 0 && ls[y][x-1] == '*' {
+		xy = append(xy, XY { x-1, y })
+	}
+
+	if x+1 < X && ls[y][x+1] == '*' {
+		xy = append(xy, XY { x+1, y })
+	}
+
+	if y+1 < Y {
+		if x > 0 && ls[y+1][x-1] == '*' {
+			xy = append(xy, XY { x-1, y+1 })
+		}
+
+		if ls[y+1][x] == '*' {
+			xy = append(xy, XY { x, y+1 })
+		}
+
+		if x+1 < X && ls[y+1][x+1] == '*' {
+			xy = append(xy, XY { x+1, y+1 })
+		}
+	}
+
+	return xy
+}
+
 func partB(fn string) {
-	var b int
+	ls := getLines(fn)
+	Y := len(ls)
+	X := len(ls[0])
+
+	Gs := make(map[XY][]int)
+	for y := 0; y < Y; y++ {
+		for x := 0; x < X; x++ {
+			if isDigit(ls[y][x]) {
+				gs := make(map[XY]bool)
+				//x0 := x
+				sum := 0
+				for ; x < X && isDigit(ls[y][x]); x++ {
+					for _, g := range adjacentGears(ls, x, y) {
+						gs[g] = true
+					}
+					sum = 10*sum + int(ls[y][x]-'0')
+				}
+				//log.Printf("(%d,%d) %v %v", x0, y, sum, gs)
+				for g, _ := range gs {
+					Gs[g] = append(Gs[g], sum)
+				}
+			}
+		}
+	}
+	b := 0
+	for _, ns := range Gs {
+		if len(ns) == 2 {
+			b += ns[0]*ns[1]
+		}
+	}
 	log.Printf("%s: %v", fn, b)
 }
 


@@ 108,6 186,6 @@ func main() {
 	partA("03.example") // 4361
 	partA("03.input") // 551094
 
-	//partB("03.example")
-	//partB("03.input")
+	partB("03.example") // 467835
+	partB("03.input") // 80179647
 }