diff --git a/.idea/workspace.xml b/.idea/workspace.xml
index 0bb4675..4b832ec 100644
--- a/.idea/workspace.xml
+++ b/.idea/workspace.xml
@@ -11,10 +11,9 @@
-
-
-
+
+
@@ -55,7 +54,7 @@
-
+
@@ -106,6 +105,15 @@
+
+
+
+
+
+
+
+
+
@@ -224,9 +232,11 @@
+
@@ -261,26 +271,26 @@
-
+
-
-
+
+
-
-
+
+
-
-
+
+
-
+
@@ -301,9 +311,9 @@
-
+
-
+
\ No newline at end of file
diff --git a/day15/day15.go b/day15/day15.go
new file mode 100644
index 0000000..b18853a
--- /dev/null
+++ b/day15/day15.go
@@ -0,0 +1,59 @@
+package main
+
+import "fmt"
+
+func main() {
+ fmt.Println(run([]int{5,1,9,18,13,8,0}, 2020))
+ fmt.Println(runPart2([]int{5,1,9,18,13,8,0}, 30000000))
+}
+
+func run(startingNumber []int, length int) int{
+ var band []int
+ band = append(band, startingNumber...)
+ for i := len(startingNumber); i < length; i++ {
+ currentNumber := band[i-1]
+ index := findIndex(currentNumber,band)
+ if index == -1 {
+ band = append(band, 0)
+ }else {
+ band = append(band, i-1-index)
+ }
+ }
+ return band[len(band)-1]
+}
+
+func runPart2(startingNumber []int, length int) int{
+ var band = make (map[int][]int)
+ for i, val := range startingNumber {
+ band[val] = []int{i,i}
+ }
+ lastNumber := startingNumber[len(startingNumber)-1]
+ for i := len(startingNumber); i < length; i++ {
+ currentNumber := lastNumber
+ indexes := band[currentNumber]
+ diffIndexes := indexes[1]-indexes[0]
+ if diffIndexes == 0 {
+ lastNumber = 0
+ band[0] = []int{band[0][1],i}
+ }else {
+ lastNumber = diffIndexes
+ if len(band[diffIndexes]) != 0 {
+ band[diffIndexes] = []int{band[diffIndexes][1],i}
+ }else {
+ band[diffIndexes] = []int{i,i}
+ }
+ }
+ }
+ return lastNumber
+}
+
+func findIndex(number int, band []int) int{
+ for i := len(band)-2; i >= 0; i-- {
+ if band[i] == number {
+ return i
+ }
+ }
+ return -1
+}
+
+
diff --git a/helper/helper.go b/helper/helper.go
index 35ce7a4..0e2eee0 100644
--- a/helper/helper.go
+++ b/helper/helper.go
@@ -56,3 +56,12 @@ func FindAddendsForSum (possibleAddends []int, sum int) (int, int, error) {
}
return 0,0,errors.New("No fitting Addends found")
}
+
+func SliceIndex(limit int, predicate func(i int) bool) int {
+ for i := 0; i < limit; i++ {
+ if predicate(i) {
+ return i
+ }
+ }
+ return -1
+}
\ No newline at end of file