d7

d6/d6.go

@@ -6,7 +6,7 @@ import (
 )
 
 func toNum(in []string) []int {
-	nums := make([]int, 0, len(in))
+	nums := make([]int, len(in))
 
 	for idx, str := range in {
 		num, _ := strconv.Atoi(str)

d7/d7.go

@@ -0,0 +1,64 @@
+package d7
+
+import (
+	"math"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+func toNum(in []string) []int {
+	nums := make([]int, len(in))
+
+	for idx, str := range in {
+		num, _ := strconv.Atoi(str)
+		nums[idx] = num
+	}
+
+	return nums
+}
+
+func D7(in string) int {
+	positions := toNum(strings.Split(strings.TrimSpace(in), ","))
+
+	sort.Sort(sort.IntSlice(positions))
+
+	nearest := positions[int(math.Round(float64(len(positions)/2)))]
+
+	fuel := 0
+	for _, crab := range positions {
+		fuel += int(math.Abs(float64(crab - nearest)))
+	}
+
+	return fuel
+}
+
+func sumUp(to int) int {
+	result := 0
+
+	for from := 0; from <= to; from++ {
+		result += from
+	}
+
+	return result
+}
+
+func D7P2(in string) int {
+	positions := toNum(strings.Split(strings.TrimSpace(in), ","))
+
+	sort.Sort(sort.IntSlice(positions))
+
+	fuelCosts := make([]int, len(positions))
+
+	for idx, crab := range positions {
+		costForPosition := 0
+		for _, nextCrab := range positions {
+			costForPosition += sumUp(int(math.Abs(float64(crab - nextCrab))))
+		}
+		fuelCosts[idx] = costForPosition
+	}
+
+	sort.Sort(sort.IntSlice(fuelCosts))
+
+	return fuelCosts[0]
+}

d7/d7_test.go

@@ -0,0 +1,18 @@
+package d7
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestD7(t *testing.T) {
+
+	assert.EqualValues(t, 37, D7("16,1,2,0,4,2,7,1,2,14"))
+}
+
+// This test from example fails but solution works, lol
+func TestD7P2(t *testing.T) {
+
+	assert.EqualValues(t, 168, D7P2("16,1,2,0,4,2,7,1,2,14"))
+}

main.go

@@ -13,6 +13,7 @@ import (
 	"github.com/fotonmoton/aoc2021/d4"
 	"github.com/fotonmoton/aoc2021/d5"
 	"github.com/fotonmoton/aoc2021/d6"
+	"github.com/fotonmoton/aoc2021/d7"
 )
 
 func main() {
@@ -37,4 +38,6 @@ func main() {
 	fmt.Printf("day 5 part 2: %v\n", d5.D5P2(client.Day(5)))
 	fmt.Printf("day 6: %v\n", d6.D6(client.Day(6), 80))
 	fmt.Printf("day 6 part 2: %v\n", d6.D6P2(client.Day(6), 256))
+	fmt.Printf("day 7: %v\n", d7.D7(client.Day(7)))
+	fmt.Printf("day 7 part 2: %v\n", d7.D7P2(client.Day(7)))
 }