complete day 13 part 1

day13/input

@@ -0,0 +1,2 @@
+1000066
+13,x,x,41,x,x,x,37,x,x,x,x,x,659,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,19,x,x,x,23,x,x,x,x,x,29,x,409,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,17

day13/input.example

@@ -0,0 +1,2 @@
+939
+7,13,x,x,59,x,31,19

day13/main.go

@@ -0,0 +1,43 @@
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"strings"
+	"strconv"
+)
+
+type Bus struct {
+	Num int
+	Arrival int
+}
+func main() {
+	d, _ := ioutil.ReadFile("input")
+	lines := strings.Split(string(d),"\n")
+	departure, _ := strconv.Atoi(lines[0]) // Earliest departure time
+	busstrings := strings.Split(lines[1],",")
+	var busses []int
+	for _, b := range busstrings {
+		if b != "x" {
+			n, _ := strconv.Atoi(b)
+			busses = append(busses, n)
+		} 
+	}
+	var bustimes []Bus
+	for _, b := range busses {
+		i := b
+		for i < departure {
+			i += b
+		}
+		bustimes = append(bustimes, Bus{Num: b, Arrival: i})
+	}
+	earliestBus := Bus{}
+	for _, bus := range bustimes {
+		if earliestBus.Num == 0 { // If we have the first real bus
+			earliestBus = bus
+		} else if earliestBus.Arrival > bus.Arrival {
+			earliestBus = bus
+		}
+	}
+	fmt.Println("Part 1:", earliestBus.Num * (earliestBus.Arrival - departure))
+}