Add day 1 in Go

2019/1/day1.go

@@ -0,0 +1,46 @@
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"strconv"
+	"strings"
+)
+
+func main() {
+	inFile, _ := ioutil.ReadFile("input")
+	lines := strings.Split(string(inFile), "\n")
+
+	fmt.Printf("Part 1: %d\n", part1(lines))
+	fmt.Printf("Part 2: %d\n", part2(lines))
+}
+
+func part1(lines []string) int {
+	fuel := 0
+	for _, line := range lines {
+		mass, _ := strconv.Atoi(line)
+		fuel += cost(mass)
+	}
+	return fuel
+}
+
+func part2(lines []string) int {
+	fuel := 0
+	for _, line := range lines {
+		mass, _ := strconv.Atoi(line)
+		fuel += costRec(mass, 0)
+	}
+	return fuel
+}
+
+func cost(mass int) int {
+	return mass/3 - 2
+}
+
+func costRec(mass int, acc int) int {
+	c := cost(mass)
+	if c <= 0 {
+		return acc
+	}
+	return costRec(c, acc+c)
+}