Started AOC 2020 - solved the first 4.5 days.

2020/day03.go

@@ -0,0 +1,44 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"git.annabunch.es/annabunches/adventofcode/2020/lib/fileutils"
+)
+
+func countTrees(input []string, right, down int) int {
+	x := 0
+	total := 0
+	for y, line := range input {
+		if y == 0 || len(line) == 0 || y%down != 0 {
+			continue
+		}
+
+		x = (x + right) % len(line)
+		if line[x] == '#' {
+			total += 1
+		}
+	}
+
+	return total
+}
+
+func main() {
+	step := os.Args[1]
+	values := fileutils.InputParserStrings(os.Args[2])
+
+	switch step {
+	case "1":
+		total := countTrees(values, 3, 1)
+		fmt.Println("Trees:", total)
+	case "2":
+		total := countTrees(values, 1, 1)
+		total *= countTrees(values, 3, 1)
+		total *= countTrees(values, 5, 1)
+		total *= countTrees(values, 7, 1)
+		total *= countTrees(values, 1, 2)
+		fmt.Println("Tree Product:", total)
+	}
+
+}