updates

2024/go/day12/day12.go

@@ -0,0 +1,146 @@
+package day12
+
+import (
+	"adventofcode2024/utils/grid2d"
+	"adventofcode2024/utils/inputs"
+	"fmt"
+
+)
+
+type Plot struct {
+	crop    string
+	visited bool
+	region  int
+	x		int
+	y 		int
+}
+
+type Region struct {
+	plots      []Plot
+	crop       string
+	id         int
+	area       int
+	perimteter int
+	sides      int
+}
+
+func Part1(input string) int {
+	var val int
+	region_id := 0
+	regions := make(map[int]Region)
+	grid := inputs.ToGrid2D(input, "\n", "", Plot{}, func(c string) Plot { return Plot{crop: c, region: -1} })
+	fmt.Println(grid.StringWithFormatter(formatter))
+	for y := 0; y < grid.SizeY(); y++ {
+		for x := 0; x < grid.SizeX(); x++ {
+			var region Region
+			plot := grid.Get(x, y)
+			if plot.visited {
+				continue
+			}
+
+			region_id++
+			region = Region{id: region_id, area: 1, crop: plot.crop, sides: 4}
+			plot.region = region_id
+			plot.visited = true
+			plot.x = x
+			plot.y = y
+			grid.Set(x, y, plot)
+			region.plots = append(region.plots, plot)
+			regions[region_id] = region
+
+			try_neighours(grid, &region, x, y)
+			regions[region.id] = region
+		}
+	}
+	for _, region := range regions {
+		val += region.area * region.perimteter
+	}
+	return val
+}
+
+func Part2(input string) int {
+	var val int
+	region_id := 0
+	regions := make(map[int]Region)
+	grid := inputs.ToGrid2D(input, "\n", "", Plot{}, func(c string) Plot { return Plot{crop: c, region: -1} })
+	fmt.Println(grid.StringWithFormatter(formatter))
+	for y := 0; y < grid.SizeY(); y++ {
+		for x := 0; x < grid.SizeX(); x++ {
+			var region Region
+			plot := grid.Get(x, y)
+			if plot.visited {
+				continue
+			}
+
+			region_id++
+			region = Region{id: region_id, area: 1, crop: plot.crop}
+			plot.region = region_id
+			plot.visited = true
+			plot.x = x
+			plot.y = y
+			grid.Set(x, y, plot)
+			region.plots = append(region.plots, plot)
+			regions[region_id] = region
+
+			try_neighours(grid, &region, x, y)
+			regions[region.id] = region
+		}
+	}
+	for _, region := range regions {
+		val += region.area * get_sides(grid, region)
+	}
+	return val
+}
+
+func formatter(p Plot, x int, y int) string {
+	return fmt.Sprintf("%v", p.crop)
+}
+
+func try_neighours(grid *grid2d.Grid[Plot], region *Region, x int, y int) {
+
+	directions := [][]int{{0, 1}, {0, -1}, {1, 0}, {-1, 0}}
+	plot := grid.Get(x, y)
+	perimeters := 0
+
+	for _, dir := range directions {
+		x1 := x + dir[0]
+		y1 := y + dir[1]
+		nplot := grid.Get(x1, y1)
+
+		if nplot.crop == plot.crop {
+			if !nplot.visited {
+				region.area++
+				nplot.visited = true
+				nplot.region = plot.region
+				nplot.x = x1
+				nplot.y = y1
+				grid.Set(x1, y1, nplot)
+				region.plots = append(region.plots, nplot)
+				try_neighours(grid, region, x1, y1)
+			}
+		} else {
+			perimeters++
+		}
+	}
+}
+
+func get_sides(grid *grid2d.Grid[Plot], region Region) int {
+	sides := 0	
+	corners := [][][]int{{{-1, 0}, {0, -1}, {-1, -1}},
+					     {{+1, 0}, {0, -1}, {+1, -1}},
+					     {{-1, 0}, {0, +1}, {-1, +1}},
+					     {{+1, 0}, {0, +1}, {+1, +1}}}
+	for _, plot := range region.plots {
+		for _, o_corners := range corners {
+				c1 := grid.Get(plot.x + o_corners[0][0], plot.y + o_corners[0][1])
+				c2 := grid.Get(plot.x + o_corners[1][0], plot.y + o_corners[1][1])
+				c3 := grid.Get(plot.x + o_corners[2][0], plot.y + o_corners[2][1])
+				if c1.crop != region.crop && c2.crop != region.crop {
+					sides++
+				} else if c1.crop == region.crop && c2.crop == region.crop && c3.crop != region.crop {
+					sides++
+				}
+		}
+	}
+	return sides
+}