Add Day15

Author: Bálint Kemény

Day15/main.go

@@ -0,0 +1,42 @@
+package main
+
+import "fmt"
+
+type memoryLoc struct {
+	current int
+	last    int
+}
+
+func main() {
+	input := []int{1, 2, 16, 19, 18, 0}
+	m := make(map[int]memoryLoc)
+
+	var previousNumber int
+	for i := 0; i < 30000000; i++ {
+		if i < len(input) {
+			m[input[i]] = memoryLoc{i, -1}
+			previousNumber = input[i]
+		} else {
+			if m[previousNumber].last == -1 {
+				_, ok := m[0]
+				if !ok {
+					m[0] = memoryLoc{i, -1}
+				} else {
+					m[0] = memoryLoc{i, m[0].current}
+				}
+				previousNumber = 0
+			} else {
+				currentNumber := m[previousNumber].current - m[previousNumber].last
+				_, ok := m[currentNumber]
+				if !ok {
+					m[currentNumber] = memoryLoc{i, -1}
+				} else {
+					m[currentNumber] = memoryLoc{i, m[currentNumber].current}
+				}
+				previousNumber = currentNumber
+			}
+		}
+	}
+
+	fmt.Println(previousNumber)
+}