day 04

04/main.go

@@ -0,0 +1,66 @@
+package main
+
+import (
+	"fmt"
+
+	"git.z1glr.de/advent-of-code-2025/pkg/aoc"
+)
+
+func testGrid(g *[][]string) int {
+	rollCount := 0
+
+	for yy, row := range *g {
+		for xx, roll := range row {
+			if roll == "@" {
+				freeCount := 0
+
+				for x := xx - 1; x <= xx+1; x++ {
+					for y := yy - 1; y <= yy+1; y++ {
+						if x < 0 || y < 0 || x >= len(row) || y >= len(*g) {
+							freeCount++
+						} else if (*g)[y][x] == "." {
+							freeCount++
+						}
+					}
+				}
+
+				if freeCount > 4 {
+					rollCount++
+
+					(*g)[yy][xx] = "x"
+				}
+			}
+		}
+	}
+
+	for yy, row := range *g {
+		for xx, roll := range row {
+			if roll != "@" {
+				(*g)[yy][xx] = "."
+			} else {
+				fmt.Print()
+			}
+		}
+	}
+
+	return rollCount
+}
+
+func main() {
+	lines := aoc.ReadFileRows(false)
+
+	grid := aoc.RowsToGrid(lines)
+
+	rollCount := testGrid(&grid)
+	fmt.Println(rollCount)
+
+	for {
+		if newCount := testGrid(&grid); newCount == 0 {
+			break
+		} else {
+			rollCount += newCount
+		}
+	}
+
+	fmt.Println(rollCount)
+}