add day 21 part 1

day21.go

@@ -0,0 +1,43 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+)
+
+func get_part1(monkeys map[string]string, monkey string) int {
+	broken := strings.Split(monkeys[monkey], " ")
+	if len(broken) == 1 {
+		yell, _ := strconv.Atoi(broken[0])
+		return yell
+	} else {
+		if broken[1] == "+" {
+			return get_part1(monkeys, broken[0]) + get_part1(monkeys, broken[2])
+		}
+		if broken[1] == "-" {
+			return get_part1(monkeys, broken[0]) - get_part1(monkeys, broken[2])
+		}
+		if broken[1] == "*" {
+			return get_part1(monkeys, broken[0]) * get_part1(monkeys, broken[2])
+		}
+		return get_part1(monkeys, broken[0]) / get_part1(monkeys, broken[2])
+	}
+}
+
+func main() {
+
+	input, _ := os.ReadFile("./input/input21.txt")
+
+	monkeys := map[string]string{}
+
+	lines := strings.Split(string(input), "\r\n")
+	for _, line := range lines {
+		broken := strings.Split(line, ": ")
+		monkeys[broken[0]] = broken[1]
+	}
+
+	fmt.Println("Part 1:", get_part1(monkeys, "root"))
+	fmt.Println("Part 2:", 0)
+}