AoC Day 21, Part 1 Solved

2023/21/code.go

@@ -0,0 +1,89 @@
+package main
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/jpillora/puzzler/harness/aoc"
+)
+
+func main() {
+	aoc.Harness(run)
+}
+
+// on code change, run will be executed 4 times:
+// 1. with: false (part1), and example input
+// 2. with: true (part2), and example input
+// 3. with: false (part1), and user input
+// 4. with: true (part2), and user input
+// the return value of each run is printed to stdout
+func run(part2 bool, input string) any {
+	grid := make([][]rune, 0)
+	v, h := 0, 0
+	for y, l := range strings.Split(input, "\n") {
+		if l == "" {
+			continue
+		}
+
+		gridLine := make([]rune, 0)
+		for x, s := range strings.Split(l, "") {
+			if s == "S" {
+				v, h = y, x
+			}
+			gridLine = append(gridLine, rune(s[0]))
+		}
+		grid = append(grid, gridLine)
+	}
+
+	steps := 64
+
+	// when you're ready to do part 2, remove this "not implemented" block
+	if part2 {
+		return "not implemented"
+	}
+	// solve part 1 here
+
+	possibleCells := [][]int{{v, h}}
+
+	for i := 0; i < steps; i++ {
+		nextStepCells := make([][]int, 0)
+		alreadyStepped := make(map[string]bool)
+
+		for _, pc := range possibleCells {
+
+			if pc[0] > 0 && grid[pc[0]-1][pc[1]] != '#' {
+				if _, ok := alreadyStepped[fmt.Sprintf("%v;%v", pc[0]-1, pc[1])]; !ok {
+					nextStepCells = append(nextStepCells, []int{pc[0] - 1, pc[1]})
+					alreadyStepped[fmt.Sprintf("%v;%v", pc[0]-1, pc[1])] = true
+				}
+			}
+
+			if pc[1] > 0 && grid[pc[0]][pc[1]-1] != '#' {
+				if _, ok := alreadyStepped[fmt.Sprintf("%v;%v", pc[0], pc[1]-1)]; !ok {
+					nextStepCells = append(nextStepCells, []int{pc[0], pc[1] - 1})
+					alreadyStepped[fmt.Sprintf("%v;%v", pc[0], pc[1]-1)] = true
+				}
+			}
+
+			if pc[0] < len(grid)-1 && grid[pc[0]+1][pc[1]] != '#' {
+				if _, ok := alreadyStepped[fmt.Sprintf("%v;%v", pc[0]+1, pc[1])]; !ok {
+					nextStepCells = append(nextStepCells, []int{pc[0] + 1, pc[1]})
+					alreadyStepped[fmt.Sprintf("%v;%v", pc[0]+1, pc[1])] = true
+				}
+			}
+
+			if pc[1] < len(grid[0])-1 && grid[pc[0]][pc[1]+1] != '#' {
+				if _, ok := alreadyStepped[fmt.Sprintf("%v;%v", pc[0], pc[1]+1)]; !ok {
+					nextStepCells = append(nextStepCells, []int{pc[0], pc[1] + 1})
+					alreadyStepped[fmt.Sprintf("%v;%v", pc[0], pc[1]+1)] = true
+				}
+			}
+
+		}
+
+		possibleCells = nextStepCells
+		//fmt.Printf("Possible steps: %v\n", possibleCells)
+	}
+
+	return len(possibleCells)
+}