From d2a16c628158993f8222d2fb303868a9af9215ea Mon Sep 17 00:00:00 2001
From: Knut Ahlers <knut@ahlers.me>
Date: Sun, 1 Dec 2019 14:28:58 +0100
Subject: [PATCH] Add solution for Day 1

---
 day01.go        |  59 ++++++++++++++++++++++++++++
 day01_input.txt | 100 ++++++++++++++++++++++++++++++++++++++++++++++++
 day01_test.go   |  44 +++++++++++++++++++++
 3 files changed, 203 insertions(+)
 create mode 100644 day01.go
 create mode 100644 day01_input.txt
 create mode 100644 day01_test.go

diff --git a/day01.go b/day01.go
new file mode 100644
index 0000000..1b1be73
--- /dev/null
+++ b/day01.go
@@ -0,0 +1,59 @@
+package aoc2019
+
+import (
+	"bufio"
+	"os"
+	"strconv"
+
+	"github.com/pkg/errors"
+)
+
+func calculateDay1FuelForMass(mass int64) int64 {
+	return mass/3 - 2
+}
+
+func calculateDay1FuelForMassRecurse(mass int64) int64 {
+	sumFuel := mass/3 - 2
+
+	var addFuel = calculateDay1FuelForMass(sumFuel)
+	for addFuel > 0 {
+		sumFuel += addFuel
+		addFuel = calculateDay1FuelForMass(addFuel)
+	}
+
+	return sumFuel
+}
+
+func solveDay1FromInput(inFile string, sumFn func(int64) int64) (int64, error) {
+	f, err := os.Open(inFile)
+	if err != nil {
+		return 0, errors.Wrap(err, "Unable to open input file")
+	}
+	defer f.Close()
+
+	var sumFuel int64
+
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		if scanner.Err() != nil {
+			return 0, errors.Wrap(err, "Unable to scan file")
+		}
+
+		mass, err := strconv.ParseInt(scanner.Text(), 10, 64)
+		if err != nil {
+			return 0, errors.Wrapf(err, "Unable to parse integer input %q", scanner.Text())
+		}
+
+		sumFuel += sumFn(mass)
+	}
+
+	return sumFuel, nil
+}
+
+func solveDay1Part1(inFile string) (int64, error) {
+	return solveDay1FromInput(inFile, calculateDay1FuelForMass)
+}
+
+func solveDay1Part2(inFile string) (int64, error) {
+	return solveDay1FromInput(inFile, calculateDay1FuelForMassRecurse)
+}
diff --git a/day01_input.txt b/day01_input.txt
new file mode 100644
index 0000000..3ddd053
--- /dev/null
+++ b/day01_input.txt
@@ -0,0 +1,100 @@
+62371
+94458
+78824
+57296
+84226
+133256
+101771
+61857
+120186
+132234
+50964
+97800
+81275
+109561
+145666
+134029
+81625
+61963
+83820
+104210
+62264
+146376
+91889
+116069
+54596
+132877
+70341
+89983
+84627
+51617
+84846
+114416
+132268
+136516
+104082
+133669
+86585
+96389
+111737
+51954
+132971
+84097
+66260
+133883
+84720
+51985
+61024
+55912
+125334
+69541
+58806
+56014
+62563
+80799
+67284
+93971
+147238
+114830
+61376
+65096
+73498
+54792
+88590
+63225
+129226
+67872
+55563
+110467
+91120
+100281
+148236
+121886
+75671
+124736
+90588
+52175
+140673
+71029
+73865
+142021
+140326
+77894
+61245
+96492
+136329
+132967
+83975
+53082
+56784
+50024
+131154
+138517
+130787
+103334
+104287
+140644
+148945
+58945
+62153
+93488
diff --git a/day01_test.go b/day01_test.go
new file mode 100644
index 0000000..5073a7c
--- /dev/null
+++ b/day01_test.go
@@ -0,0 +1,44 @@
+package aoc2019
+
+import "testing"
+
+func TestCalculateDay1_Examples(t *testing.T) {
+	for mass, expFuel := range map[int64]int64{
+		12:     2,
+		14:     2,
+		1969:   654,
+		100756: 33583,
+	} {
+		if f := calculateDay1FuelForMass(mass); f != expFuel {
+			t.Errorf("Mismatch for mass of %d, expected %d, got %d", mass, expFuel, f)
+		}
+	}
+
+	for mass, expFuel := range map[int64]int64{
+		14:     2,
+		1969:   966,
+		100756: 50346,
+	} {
+		if f := calculateDay1FuelForMassRecurse(mass); f != expFuel {
+			t.Errorf("Mismatch in recurse for mass of %d, expected %d, got %d", mass, expFuel, f)
+		}
+	}
+}
+
+func TestCalculateDay1_Part1(t *testing.T) {
+	fuel, err := solveDay1Part1("day01_input.txt")
+	if err != nil {
+		t.Fatalf("Day 1 solver failed: %s", err)
+	}
+
+	t.Logf("Solution Day 1 Part 1: %d", fuel)
+}
+
+func TestCalculateDay1_Part2(t *testing.T) {
+	fuel, err := solveDay1Part2("day01_input.txt")
+	if err != nil {
+		t.Fatalf("Day 1 solver failed: %s", err)
+	}
+
+	t.Logf("Solution Day 1 Part 2: %d", fuel)
+}