D1: implement puzzle part 2 solution

day01/day01.go

@@ -0,0 +1,78 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"strconv"
+)
+
+func main() {
+	inputFile, err := os.OpenFile("input", os.O_RDWR, 0666)
+	if err != nil {
+		log.Fatalf("error reading input data %v", err)
+	}
+	fmt.Printf("The elf with the most calories has %d calories\n", findMostCalories(inputFile))
+	inputFile.Seek(0, 0)
+	top3 := findTopThree(inputFile)
+	sum := 0
+	for _, n := range top3 {
+		sum += n
+	}
+	fmt.Printf("The three elves with the most calories together have %d calories\n", sum)
+}
+
+func findMostCalories(input io.Reader) int {
+	r := bufio.NewScanner(input)
+	var maxSeen, calories int
+	for r.Scan() {
+		if r.Text() == "" {
+			if calories > maxSeen {
+				maxSeen = calories
+			}
+			calories = 0
+		} else {
+			toAdd, err := strconv.Atoi(r.Text())
+			if err != nil {
+				log.Fatalf("could not interpret data as calories: %v", err)
+			}
+			calories += toAdd
+		}
+	}
+	return maxSeen
+}
+
+func findTopThree(input io.Reader) []int {
+	r := bufio.NewScanner(input)
+	var calories int
+	top := []int{0, 0, 0}
+
+	for r.Scan() {
+		if r.Text() == "" {
+			for i := range top {
+				if calories > top[i] {
+					tmp := top[i]
+					top[i] = calories
+					calories = tmp
+				}
+			}
+			calories = 0
+		} else {
+			toAdd, err := strconv.Atoi(r.Text())
+			if err != nil {
+				log.Fatalf("could not interpret data as calories: %v", err)
+			}
+			calories += toAdd
+		}
+	}
+	for i := range top {
+		if calories > top[i] {
+			tmp := top[i]
+			top[i] = calories
+			calories = tmp
+		}
+	}
+	return top
+}

day_1/day_1_test.go → day01/day01_test.go

@@ -6,8 +6,7 @@ import (
 )
 
 func TestFindMostCalories(t *testing.T) {
-	t.Run("basic case", func(t *testing.T) {
-		input := strings.NewReader(`1000
+	input := strings.NewReader(`1000
 2000
 3000
 
@@ -21,9 +20,23 @@ func TestFindMostCalories(t *testing.T) {
 9000
 
 10000`)
+
+	t.Run("basic case", func(t *testing.T) {
 		answer := findMostCalories(input)
 		if answer != 24000 {
 			t.Errorf("want answer 24000, got %v", answer)
 		}
 	})
+
+	t.Run("find top three", func(t *testing.T) {
+		input.Seek(0, 0)
+		answer := findTopThree(input)
+		want := []int{24000, 11000, 10000}
+		for i := range want {
+			if answer[i] != want[i] {
+				t.Errorf("want answer %v, got %v", want, answer)
+				break
+			}
+		}
+	})
 }

day01/go.mod

@@ -0,0 +1,3 @@
+module aoc_day01
+
+go 1.19