2017 Day 10 Part 1

2017/day10.py

@@ -0,0 +1,31 @@
+with open("input/day10.txt") as f:
+    size, input = 256, f.read().strip()
+
+lengths = [int(i) for i in input.split(",")]
+
+ring = list(range(size))
+pos = 0
+skip = 0
+
+for length in lengths:
+    assert length <= len(ring), "overlap undefined"
+
+    tail = min(length, len(ring) - pos)
+    head = max(length - tail, 0)
+
+    a = pos + tail
+    b = 0 + head
+
+    prefix = ring[b:pos]
+    inside = ring[pos:a] + ring[:b]
+    suffix = ring[a:]
+
+    assert length == len(inside)
+
+    twisted = inside[::-1]
+
+    ring = twisted[tail:] + prefix + twisted[:tail] + suffix
+    pos = (pos + length + skip) % len(ring)
+    skip += 1
+
+print(ring[0] * ring[1])