2016: d16: ex2: add solution

2016/d16/ex2/ex2.py

@@ -0,0 +1,30 @@
+#!/usr/bin/env python
+
+import itertools
+import sys
+
+
+def solve(input: str) -> str:
+    def curve_step(input: str) -> str:
+        b = input.translate(str.maketrans("01", "10"))[::-1]
+        return input + "0" + b
+
+    def checksum(state: str) -> str:
+        while len(state) % 2 == 0:
+            state = "".join(str(int(a == b)) for a, b in itertools.batched(state, 2))
+        return state
+
+    state = input.strip()
+    disk_size = 35651584
+    while len(state) < disk_size:
+        state = curve_step(state)
+    return checksum(state[:disk_size])
+
+
+def main() -> None:
+    input = sys.stdin.read()
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()