2018 Day 9

Author: Programator2

2018/9a.py

@@ -0,0 +1,39 @@
+import collections
+
+PLAYERS = 400
+LAST_MARBLE = 7186400  # points
+
+
+class MarbleDesk(collections.UserList):
+    def __getitem__(self, x):
+        return self.data[x % len(self)]
+
+    # def insert(self, i, x):
+    #     " Insert before the i-th element "
+    #     return self.data.insert(i % len(self), x)
+
+    # def pop(self, i):
+    #     return self.data.pop(i % len(self))
+
+
+m = collections.deque([0])
+current = 0
+# I index players from zero, in the text they start at 1
+player = 0
+scoreboard = collections.defaultdict(int)
+
+for next_marble in range(1, LAST_MARBLE + 1):
+    if next_marble % 23:
+        # normal run
+        insert_index = (current + 2) % len(m)
+        m.insert(insert_index, next_marble)
+        current = insert_index
+    else:
+        # special case
+        scoreboard[player] += next_marble
+        pop_index = (current - 7) % len(m)
+        scoreboard[player] += m.pop(pop_index)
+        current = (pop_index) % len(m)
+    player = (player + 1) % PLAYERS
+
+print(max(scoreboard.values()))

2018/9b.py

@@ -0,0 +1,59 @@
+import collections
+
+PLAYERS = 400
+LAST_MARBLE = 7186400  # points
+
+
+class Node:
+    def __init__(self, num):
+        self.num = num
+        self.prev = None
+        self.next = None
+
+    def insert_after(self, n, new_node):
+        node = self
+        for i in range(n):
+            node = node.next
+        old_next = node.next
+        node.next = new_node
+        old_next.prev = new_node
+        new_node.next = old_next
+        new_node.prev = node
+
+    def prev_n(self, n):
+        node = self
+        for i in range(n):
+            node = node.prev
+        return node
+
+    def remove(self):
+        self.prev.next = self.next
+        self.next.prev = self.prev
+        after_this = self.next
+        self.next = None
+        self.prev = None
+        return self.num, after_this
+
+
+m = Node(0)
+m.prev = m
+m.next = m
+current = m
+# I index players from zero, in the text they start at 1
+player = 0
+scoreboard = collections.defaultdict(int)
+
+for next_marble in range(1, LAST_MARBLE + 1):
+    if next_marble % 23:
+        # normal run
+        n = Node(next_marble)
+        current.insert_after(1, n)
+        current = n
+    else:
+        # special case
+        scoreboard[player] += next_marble
+        score, current = current.prev_n(7).remove()
+        scoreboard[player] += score
+    player = (player + 1) % PLAYERS
+
+print(max(scoreboard.values()))