Solution for Day 9

nine/vents.go

@@ -0,0 +1,176 @@
+package nine
+
+import (
+	"bufio"
+	"os"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+type vents struct {
+	floor     [][]int
+	counted   [][]bool
+	lowPoints *[]basin
+}
+
+type basin struct {
+	lowPoint int
+	size     int
+}
+
+func (v *vents) load(filename string) error {
+	file, err := os.Open(filename)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+
+	v.floor = [][]int{}
+	v.counted = [][]bool{}
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		elements := []int{}
+
+		heights := strings.Split(scanner.Text(), "")
+
+		counts := make([]bool, len(heights))
+
+		for _, h := range heights {
+			v, err := strconv.Atoi(h)
+			if err != nil {
+				return nil
+			}
+			elements = append(elements, v)
+		}
+
+		v.floor = append(v.floor, elements)
+		v.counted = append(v.counted, counts)
+	}
+	return nil
+}
+
+func (v *vents) findLowPoints() []basin {
+	if v.lowPoints != nil {
+		return *v.lowPoints
+	}
+
+	lowPoints := []basin{}
+
+	if len(v.floor) == 0 || len(v.floor[0]) == 0 {
+		return lowPoints
+	}
+
+	horizontal := len(v.floor[0])
+	vertical := len(v.floor)
+
+	for y := 0; y < vertical; y++ {
+		for x := 0; x < horizontal; x++ {
+			minimum := true
+			//Check above
+			if y > 0 {
+				if v.floor[y][x] >= v.floor[y-1][x] {
+					minimum = false
+				}
+			}
+
+			//Check below
+			if y < vertical-1 {
+				if v.floor[y][x] >= v.floor[y+1][x] {
+					minimum = false
+				}
+			}
+
+			//Check left
+			if x > 0 {
+				if v.floor[y][x] >= v.floor[y][x-1] {
+					minimum = false
+				}
+			}
+
+			//Check left
+			if x < horizontal-1 {
+				if v.floor[y][x] >= v.floor[y][x+1] {
+					minimum = false
+				}
+			}
+
+			if minimum {
+				b := basin{
+					lowPoint: v.floor[y][x],
+					size:     v.basinSize(x, y),
+				}
+				lowPoints = append(lowPoints, b)
+			}
+		}
+	}
+
+	v.lowPoints = &lowPoints
+	return lowPoints
+}
+
+func (v *vents) basinSize(x int, y int) int {
+	size := 1
+
+	v.counted[y][x] = true
+
+	if v.floor[y][x] == 9 {
+		return 0
+	}
+
+	horizontal := len(v.floor[0])
+	vertical := len(v.floor)
+
+	//Check above
+	if y > 0 && !v.counted[y-1][x] {
+		if v.floor[y][x] < v.floor[y-1][x] {
+			size += v.basinSize(x, y-1)
+		}
+	}
+
+	//Check below
+	if y < vertical-1 && !v.counted[y+1][x] {
+		if v.floor[y][x] < v.floor[y+1][x] {
+			size += v.basinSize(x, y+1)
+		}
+	}
+
+	//Check left
+	if x > 0 && !v.counted[y][x-1] {
+		if v.floor[y][x] < v.floor[y][x-1] {
+			size += v.basinSize(x-1, y)
+		}
+	}
+
+	//Check left
+	if x < horizontal-1 && !v.counted[y][x+1] {
+		if v.floor[y][x] < v.floor[y][x+1] {
+			size += v.basinSize(x+1, y)
+		}
+	}
+
+	return size
+}
+
+func (v *vents) sumLowPointRisk() (sum int) {
+	for _, b := range v.findLowPoints() {
+		sum += (b.lowPoint + 1)
+	}
+
+	return sum
+}
+
+func (v *vents) productLargestBasins() int {
+	sizes := sort.IntSlice{}
+	for _, b := range v.findLowPoints() {
+		sizes = append(sizes, b.size)
+	}
+
+	sort.Sort(sizes)
+
+	if len(sizes) < 3 {
+		return 0
+	}
+
+	return sizes[len(sizes)-1] * sizes[len(sizes)-2] * sizes[len(sizes)-3]
+}