day 12 part 1 solution and not working part 2

solutions/alessio/day12/day12.go

@@ -0,0 +1,168 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"sort"
+	"strings"
+	"time"
+)
+
+func check(e error) {
+	if e != nil {
+		panic(e)
+	}
+}
+
+func checkInBounds(cell Cell, rows int, cols int) bool {
+	return cell.r >= 0 && cell.r < rows && cell.c >= 0 && cell.c < cols
+}
+
+type Cell struct {
+	r, c int
+}
+
+func dfs(curr Cell, lines []string, rows int, cols int, visited *map[Cell]bool, region *[]Cell) {
+	dirs := [][]int{{0, 1}, {0, -1}, {1, 0}, {-1, 0}}
+
+	(*visited)[curr] = true
+	*region = append(*region, curr)
+	for _, dir := range dirs {
+		next := Cell{curr.r + dir[0], curr.c + dir[1]}
+		if checkInBounds(next, rows, cols) &&
+			lines[next.r][next.c] == lines[curr.r][curr.c] &&
+			!(*visited)[next] {
+			dfs(next, lines, rows, cols, visited, region)
+		}
+	}
+}
+
+func computePerimeter(r []Cell, grid []string, rows int, cols int) int {
+	symbol := grid[r[0].r][r[0].c]
+
+	perimeter := 0
+	for _, cell := range r {
+		for _, dir := range [][]int{{0, 1}, {0, -1}, {1, 0}, {-1, 0}} {
+			next := Cell{cell.r + dir[0], cell.c + dir[1]}
+			if !checkInBounds(next, rows, cols) || grid[next.r][next.c] != symbol {
+				perimeter++
+			}
+		}
+	}
+
+	return perimeter
+}
+
+const (
+	N = iota
+	E
+	S
+	W
+)
+
+type vertKey struct {
+	col, dir int
+}
+
+type horizKey struct {
+	row, dir int
+}
+
+func countSides(r []Cell, grid []string, rows int, cols int) int {
+	symbol := grid[r[0].r][r[0].c]
+	dirs := [][]int{{-1, 0}, {0, 1}, {1, 0}, {0, -1}} // N, E, S, W
+	vertSides := make(map[vertKey][]int)
+	horizSides := make(map[horizKey][]int)
+	for _, cell := range r {
+		for d, dir := range dirs {
+			next := Cell{cell.r + dir[0], cell.c + dir[1]}
+			if !checkInBounds(next, rows, cols) || grid[next.r][next.c] != symbol {
+				// perimetral cell
+				if d == N {
+					horizSides[horizKey{cell.r, d}] = append(horizSides[horizKey{cell.r, d}], cell.c)
+				} else if d == S {
+					horizSides[horizKey{cell.r + 1, d}] = append(horizSides[horizKey{cell.r + 1, d}], cell.c)
+				} else if d == W {
+					vertSides[vertKey{cell.c, d}] = append(vertSides[vertKey{cell.c, d}], cell.r)
+				} else {
+					vertSides[vertKey{cell.c + 1, d}] = append(vertSides[vertKey{cell.c + 1, d}], cell.r)
+				}
+			}
+		}
+	}
+
+	cnt := 0
+	for _, v := range horizSides {
+		sort.Ints(v)
+		for i := 1; i < len(v); i++ {
+			if v[i]-v[i-1] > 1 {
+				cnt++
+			}
+		}
+		cnt++
+	}
+
+	for _, v := range vertSides {
+		sort.Ints(v)
+		for i := 1; i < len(v); i++ {
+			if v[i]-v[i-1] > 1 {
+				cnt++
+			}
+		}
+		cnt++
+	}
+
+	return cnt
+}
+
+func solve(grid []string, useSides bool) {
+	visited := make(map[Cell]bool)
+	regions := make([][]Cell, 0)
+	rows, cols := len(grid), len(grid[0])
+	for r := range rows {
+		for c := range cols {
+			if !visited[Cell{r, c}] {
+				region := make([]Cell, 0)
+				dfs(Cell{r, c}, grid, rows, cols, &visited, &region)
+				regions = append(regions, region)
+			}
+		}
+	}
+
+	res := 0
+	for _, r := range regions {
+		area := len(r)
+		perimeter := 0
+		if !useSides {
+			perimeter = computePerimeter(r, grid, rows, cols)
+		} else {
+			perimeter = countSides(r, grid, rows, cols)
+			fmt.Printf("- A region of %c plants with price %d * %d = %d\n", grid[r[0].r][r[0].c], area, perimeter, area*perimeter)
+		}
+		res += area * perimeter
+	}
+
+	fmt.Println(res)
+}
+
+func part1(grid []string) {
+	solve(grid, false)
+}
+
+func part2(grid []string) {
+	solve(grid, true)
+}
+
+func main() {
+	data, err := os.ReadFile("./input12.txt")
+	check(err)
+	dataStr := strings.ReplaceAll(string(data), "\r\n", "\n")
+	lines := strings.Split(strings.Trim(dataStr, "\n"), "\n")
+
+	start := time.Now()
+	part1(lines)
+	fmt.Printf("part1: %s\n", time.Since(start))
+	start = time.Now()
+	part2(lines)
+	fmt.Printf("part2: %s\n", time.Since(start))
+}

solutions/alessio/day12/go.mod

@@ -0,0 +1,10 @@
+module aoc12
+
+go 1.23
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/stretchr/testify v1.10.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

solutions/alessio/day12/go.sum

@@ -0,0 +1,9 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
+github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

solutions/alessio/day12/input12.txt

@@ -0,0 +1,10 @@
+RRRRIICCFF
+RRRRIICCCF
+VVRRRCCFFF
+VVRCCCJFFF
+VVVVCJJCFE
+VVIVCCJJEE
+VVIIICJJEE
+MIIIIIJJEE
+MIIISIJEEE
+MMMISSJEEE