Add day 15 part 1

day15/main.go

@@ -0,0 +1,53 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"strings"
+)
+
+func main() {
+	if len(os.Args) != 2 && len(os.Args) != 3 {
+		fmt.Fprintf(os.Stderr, "Usage: %s inputfile\n", os.Args[0])
+		os.Exit(1)
+	}
+
+	inputFilename := os.Args[1]
+	inputFile, err := os.Open(inputFilename)
+	if err != nil {
+		panic(fmt.Sprintf("could not open input file: %s", err))
+	}
+
+	defer inputFile.Close()
+
+	inputBytes, err := io.ReadAll(inputFile)
+	if err != nil {
+		panic(fmt.Sprintf("could not read input file: %s", err))
+	}
+
+	input := strings.TrimSpace(string(inputBytes))
+	inputElements := strings.Split(input, ",")
+
+	fmt.Printf("Part 1: %d\n", part1(inputElements))
+}
+
+func part1(inputElements []string) int {
+	sum := 0
+	for _, element := range inputElements {
+		sum += hash(element)
+	}
+
+	return sum
+}
+
+func hash(s string) int {
+	res := 0
+	for _, char := range s {
+		res += int(char)
+		res *= 17
+		res %= 256
+	}
+
+	return res
+}