day-6

day-6/go.mod

@@ -0,0 +1,3 @@
+module github.com/onyx-and-iris/aoc2023/day-6
+
+go 1.20

day-6/one.go

@@ -0,0 +1,39 @@
+package main
+
+type data struct {
+	time     int
+	distance int
+}
+
+var datas = make([]data, 0)
+
+// calculate returns the number of different ways to win a single race
+func calculate(time, recordDistance int) int {
+	distanceCovered := 0
+	numWins := 0
+
+	f := func(x, time int) int {
+		return x * (time - x)
+	}
+
+	for i := 1; i < time; i++ {
+		distanceCovered = f(i, time)
+		if distanceCovered > recordDistance {
+			numWins++
+		}
+	}
+	return numWins
+}
+
+// one returns the product of all race calculations
+func one(lines []string) int {
+	parseLines(lines)
+
+	product := 1
+	for _, data := range datas {
+		n := calculate(data.time, data.distance)
+		product *= n
+	}
+
+	return product
+}

day-6/one_test.go

@@ -0,0 +1,16 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/go-playground/assert"
+)
+
+func TestCalculate(t *testing.T) {
+	//t.Skip("skipping test")
+	res := calculate(7, 9)
+
+	t.Run("Should produce an equal number of win possibilities", func(t *testing.T) {
+		assert.Equal(t, []int{2, 3, 4, 5}, res)
+	})
+}

day-6/solution.go

@@ -0,0 +1,21 @@
+package main
+
+import (
+	"fmt"
+
+	log "github.com/sirupsen/logrus"
+)
+
+func init() {
+	log.SetLevel(log.DebugLevel)
+}
+
+func main() {
+	lines := readlines()
+
+	ans := one(lines)
+	fmt.Printf("solution one: %d\n", ans)
+
+	ans = two(lines)
+	fmt.Printf("solution two: %d\n", ans)
+}

day-6/two.go

@@ -0,0 +1,34 @@
+package main
+
+import (
+	"fmt"
+	"math"
+	"strconv"
+)
+
+// calculateFaster uses quadratic formula to calculate number of ways to win
+func calculateFaster(time, recordDistance int) int {
+	a := float64(-1)
+	b := float64(time)
+	c := float64(-(recordDistance + 1))
+
+	x1 := (-b + math.Sqrt(math.Pow(b, 2)-4*a*c)) / (2 * a)
+	x2 := (-b - math.Sqrt(math.Pow(b, 2)-4*a*c)) / (2 * a)
+
+	return int(math.Floor(x2) - math.Ceil(x1) + 1)
+}
+
+func two(lines []string) int {
+	timeStr := ""
+	distStr := ""
+	for _, data := range datas {
+		timeStr += fmt.Sprintf("%d", data.time)
+		distStr += fmt.Sprintf("%d", data.distance)
+	}
+	time, _ := strconv.Atoi(timeStr)
+	distance, _ := strconv.Atoi(distStr)
+
+	n := calculateFaster(time, distance)
+
+	return n
+}

day-6/util.go

@@ -0,0 +1,57 @@
+package main
+
+import (
+	"bufio"
+	"log"
+	"os"
+	"strconv"
+	"strings"
+	"unicode"
+)
+
+// readlines reads lines from stdin.
+// Then it returns them as an array of strings
+func readlines() []string {
+	lines := []string{}
+
+	scanner := bufio.NewScanner(os.Stdin)
+	for scanner.Scan() {
+		lines = append(lines, scanner.Text())
+	}
+
+	if err := scanner.Err(); err != nil {
+		log.Fatal(err)
+	}
+
+	return lines
+}
+
+func parseLines(lines []string) {
+	f := func(c rune) bool {
+		return !unicode.IsDigit(c)
+	}
+
+	times := []int{}
+	distances := []int{}
+	for _, line := range lines {
+		if strings.HasPrefix(line, "Time") {
+			times = convertToInts(strings.FieldsFunc(line, f))
+		} else {
+			distances = convertToInts(strings.FieldsFunc(line, f))
+		}
+	}
+
+	for i := range times {
+		datas = append(datas, data{time: times[i], distance: distances[i]})
+	}
+}
+
+// convertToInts converts a string representing ints to an array of ints
+func convertToInts(data []string) []int {
+	nums := []int{}
+	for _, elem := range data {
+		n, _ := strconv.Atoi(elem)
+		nums = append(nums, n)
+	}
+	return nums
+}