2016: d19: ex2: add solution

2016/d19/ex2/ex2.py

@@ -0,0 +1,31 @@
+#!/usr/bin/env python
+
+import collections
+import sys
+
+
+def solve(input: str) -> int:
+    def white_elephant(num_elves: int) -> int:
+        left = collections.deque(range(1, (num_elves // 2) + 1))
+        right = collections.deque(range(num_elves, (num_elves // 2), -1))
+
+        while left and right:
+            if len(left) > len(right):
+                left.pop()
+            else:
+                right.pop()
+            right.appendleft(left.popleft())
+            left.append(right.pop())
+        return (left + right)[0]
+
+    num_elves = int(input.strip())
+    return white_elephant(num_elves)
+
+
+def main() -> None:
+    input = sys.stdin.read()
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()