Solved part 2 of day 15

15/part2.py

@@ -0,0 +1,24 @@
+
+
+def getStartingNumbers(filename):
+	with open(filename, "r") as f:
+		return [int(n) for n in f.read().split(",")]
+
+numbers = getStartingNumbers("input.txt")
+occurences = {n: [i] for i,n in enumerate(numbers)}
+lastNumber = numbers[-1]
+#         30000000
+targetI = 30000000
+i = len(numbers)-1
+while i+1 < targetI:
+	if len(occurences[lastNumber]) > 1:
+		number = occurences[lastNumber][-1] - occurences[lastNumber][-2]
+	else:
+		number = 0
+	i += 1
+	occurences[number] = occurences.get(number, [])
+	occurences[number].append(i)
+	occurences[number] = occurences[number][-2:]
+	lastNumber = number
+
+print(lastNumber)