Add day 9

Day9/Day9.py

@@ -0,0 +1,30 @@
+from sys import argv, exit
+from blist import blist
+
+try:
+    PLAYER_COUNT = int(argv[1])
+    LAST_MARBLE = int(argv[2])
+except (IndexError, ValueError):
+    print(f"Usage: {argv[0]} [player_count] [marble_count]")
+    exit(1)
+
+marbles = blist([0, 2, 1])
+current_id = 1
+
+scores = [0] * PLAYER_COUNT
+player = 2
+
+for next_marble in range(3, LAST_MARBLE + 1):
+    if next_marble % 23 == 0:
+        current_id = (current_id - 7) % len(marbles)
+        scores[player] += next_marble + marbles.pop(current_id)
+    else:
+        current_id += 2
+        if current_id > len(marbles):
+            current_id %= len(marbles)
+
+        marbles.insert(current_id, next_marble)
+
+    player = (player + 1) % PLAYER_COUNT
+
+print(max(scores))