day 10 part 1 overkill

2023/day10/main.go

@@ -0,0 +1,149 @@
+package main
+
+import (
+	_ "embed"
+	"flag"
+	"fmt"
+	"strings"
+
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+//go:embed input.txt
+var input string
+
+func init() {
+	// do this in init (not main) so test file has same input
+	input = strings.TrimRight(input, "\n")
+	if len(input) == 0 {
+		panic("empty input.txt file")
+	}
+}
+
+func main() {
+	var part int
+	flag.IntVar(&part, "part", 1, "part 1 or 2")
+	flag.Parse()
+	fmt.Println("Running part", part)
+
+	ans := pipeMaze(input, part)
+	util.CopyToClipboard(fmt.Sprintf("%v", ans))
+	fmt.Println("Output:", ans)
+}
+
+var pipes = map[string][2][2]int{
+	"|": {
+		{-1, 0}, // up
+		{1, 0},  // down
+	},
+	"-": {
+		{0, -1}, // left
+		{0, 1},  //right
+	},
+	"L": {
+		{-1, 0}, // up
+		{0, 1},  // right
+	},
+	"J": {
+		{-1, 0}, // up
+		{0, -1}, // left
+	},
+	"7": {
+		{0, -1}, // left
+		{1, 0},  // down
+	},
+	"F": {
+		{0, 1}, // right
+		{1, 0}, // down
+	},
+}
+
+func pipeMaze(input string, part int) int {
+	grid := parseInput(input)
+
+	var r, c int
+	for i, row := range grid {
+		for j, val := range row {
+			if val == "S" {
+				r = i
+				c = j
+			}
+		}
+	}
+
+	// need to find which directions are connected to the initial cell
+	// could traverse along the four directions and see which two lead back to
+	// the start... all pipes only connect two coordinates so it's actually
+	// fairly easy to traverse without creating a huge search space
+
+	// note this soultion was overkill for part 1
+	// inputs are nice and exactly two adjacent cells that connect to S
+	var loopCoords map[[2]int]bool
+	for pipeType := range pipes {
+		// assign the start square to a random pipeType, then see if it will loop
+		grid[r][c] = pipeType
+
+		seen := map[[2]int]bool{}
+		toAnalyze := [][2]int{
+			{r, c},
+		}
+		didLoop := false
+		for len(toAnalyze) > 0 {
+			coords := toAnalyze[0]
+			if seen[coords] {
+				didLoop = true
+				break
+			}
+			seen[coords] = true
+			toAnalyze = toAnalyze[1:]
+
+			if diffs, ok := pipes[grid[coords[0]][coords[1]]]; ok {
+				for _, diff := range diffs {
+					nextRow, nextCol := coords[0]+diff[0], coords[1]+diff[1]
+					if isInRange(grid, nextRow, nextCol) && !seen[[2]int{nextRow, nextCol}] {
+						toAnalyze = append(toAnalyze, [2]int{nextRow, nextCol})
+					}
+				}
+			}
+
+		}
+		if didLoop {
+			loopCoords = seen
+			break
+		}
+	}
+
+	if part == 1 {
+		return len(loopCoords) / 2
+	}
+
+	// part 2
+
+	newGrid := make([][]string, len(grid))
+	for i := 0; i < len(grid); i++ {
+		for j := 0; j < len(grid[0]); j++ {
+			if loopCoords[[2]int{i, j}] {
+				newGrid[i] = append(newGrid[i], grid[i][j])
+			} else {
+				newGrid[i] = append(newGrid[i], ".")
+			}
+		}
+	}
+
+	for _, r := range newGrid {
+		fmt.Println(r)
+	}
+
+	return -1
+}
+
+func isInRange(grid [][]string, row, col int) bool {
+	return row >= 0 && row < len(grid) && col >= 0 && col <= len(grid)
+}
+
+func parseInput(input string) (ans [][]string) {
+	for _, line := range strings.Split(input, "\n") {
+		ans = append(ans, strings.Split(line, ""))
+	}
+	return ans
+}