Day 17.

17.py

@@ -0,0 +1,16 @@
+with open('data/17.txt', 'r') as file:
+    steps = int(file.readline().strip())
+    buffer = []
+    position = 0
+    for i in range(2018):
+        buffer.insert(position, i)
+        position = (position + steps + 1) % (i + 1)
+    print(f'Part one: {buffer[(buffer.index(2017) + 1) % len(buffer)]}')
+
+    # The entry for zero is always at the end of our buffer, as we never call insert beyond the length of the list,
+    # so the entry after zero is always the one at position 0.
+    for i in range(2018, 50000001):
+        if position == 0:
+            after_zero = i
+        position = (position + steps + 1) % (i + 1)
+    print(f'Part two: {after_zero}')

data/17.txt

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+355