break the chain

2020/23/run.py

@@ -0,0 +1,88 @@
+from aocd import get_data
+from dataclasses import dataclass
+
+
+@dataclass
+class CrabCups:
+    cups: list
+    label: int
+    pickup = []
+    moves = 0
+
+    def move(self):
+        self.moves += 1
+        idx = self.cups.index(self.label)
+        while len(self.pickup) < 3:
+            if len(self.cups) > idx + 1:
+                self.pickup += [self.cups.pop(idx + 1)]
+            else:
+                self.pickup += [self.cups.pop(0)]
+        dest = False
+        label = self.label
+        while not dest:
+            dest = label - 1
+            if dest < 1:
+                dest = max(self.cups)
+            if dest in self.pickup:
+                dest = False
+                label -= 1
+        dest = self.cups.index(dest)
+        while self.pickup:
+            p = self.pickup.pop()
+            self.cups.insert(dest+1, p)
+        new_idx = self.cups.index(self.label) + 1
+        self.label = self.cups[new_idx % len(self.cups)]
+
+    def get_order(self):
+        order = self.cups[self.cups.index(1)+1:] + self.cups[:self.cups.index(1)]
+        return ''.join([str(o) for o in order])
+
+
+def move_cup(at, cups):
+    a = cups[at]
+    b = cups[a]
+    c = cups[b]
+    dest = at - 1
+    if dest <= 0:
+        dest = len(cups)
+    while dest in [a, b, c]:
+        dest -= 1
+        if dest <= 0:
+            dest = len(cups)
+    d = cups[dest]
+    cups[at] = cups[c]
+    cups[dest] = a
+    cups[c] = d
+    return cups[at]
+
+
+def solve_part_a(data):
+    cups = [int(c) for c in data]
+    game = CrabCups(cups=cups, label=cups[0])
+    for _ in range(100):
+        game.move()
+    return game.get_order()
+
+
+def solve_part_b(data):
+    cups = [int(c) for c in data] + list(range(10, 1_000_001))
+    cups = {n: r for n, r in zip(cups, cups[1:] + cups[:1])}
+    at = int(data[0])
+    for step in range(10_000_000):
+        at = move_cup(at, cups)        
+    a = cups[1]
+    b = cups[a]
+    return a * b
+
+
+if __name__ == "__main__":
+    data = get_data(year=2020, day=23)
+    print("-"*40)
+    print("Part 1:")
+    a = solve_part_a(data)
+    print(a)
+    print("-"*40)
+    print("Part 2:")
+    b = solve_part_b(data)
+    print(b)
+

2020/25/run.py

@@ -0,0 +1,43 @@
+from aocd import get_data
+
+
+def handshake(num, loop_size):
+    denom = 20201227
+    value = 1
+    for _ in range(loop_size):
+        value = (value * num) % denom
+    return value
+
+
+def crack_loop_size(key):
+    value = 1
+    denom = 20201227
+    num = 7
+    loop = 0
+    while True:
+        loop += 1
+        value = (value * num) % denom
+        if value == key:
+            return loop
+
+
+def solve_part_a(data):
+    a, b = [int(d) for d in data.splitlines()]
+    a_loop_size = crack_loop_size(a)
+    b_loop_size = crack_loop_size(b)
+    return handshake(a, b_loop_size)
+
+
+def solve_part_b(data):
+    pass
+
+
+if __name__ == "__main__":
+    data = get_data(year=2020, day=25)
+    print("Part 1:")
+    a = solve_part_a(data)
+    print(a)
+    print("Part 2:")
+    b = solve_part_b(data)
+    print(b)
+