AoC 2024 day 11 part 1

aoc2024/src/day11/python/solution.py

@@ -0,0 +1,67 @@
+# Copyright 2024 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+class Stone:
+  def __init__(self, value: int, next_stone=None):
+    self.value: int = value
+    self.next: Stone | None = next_stone
+
+
+class Simulation:
+  def __init__(self, initial_state: str):
+    self._first_stone = self._parse(initial_state)
+
+  def _parse(self, initial_state: str) -> Stone:
+    stones = initial_state.split()
+    first = Stone(value=int(stones[0]))
+    prev = first
+    for i in range(1, len(stones)):
+      curr = Stone(value=int(stones[i]))
+      prev.next = curr
+      prev = curr
+    return first
+
+  def blink(self):
+    curr = self._first_stone
+    while curr is not None:
+      if curr.value == 0:
+        curr.value = 1
+      elif len(str(curr.value)) % 2 == 0:  # Even num of digits:
+        half_digits = len(str(curr.value)) // 2
+        # Break stone into 2:
+        first_value = str(curr.value)[:half_digits]
+        second_value = str(curr.value)[half_digits:]
+        second_stone = Stone(value=int(second_value), next_stone=curr.next)
+        curr.value = int(first_value)
+        curr.next = second_stone
+        curr = second_stone  # Careful, should not handle the second stone.
+      else:
+        curr.value *= 2024
+      curr = curr.next
+
+  def count_stones(self) -> int:
+    # Traverse stones from first.
+    num_stones = 0
+    curr = self._first_stone
+    while curr is not None:
+      num_stones += 1
+      curr = curr.next
+    return num_stones
+
+
+def count_stones(initial_state: str, blinks: int = 0) -> int:
+  simulation = Simulation(initial_state)
+  for _ in range(blinks):
+    simulation.blink()
+  return simulation.count_stones()

aoc2024/test/day11/python/test_solution.py

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+# Copyright 2024 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import unittest
+
+from common.python3.AdventOfCodeTestCase import AdventOfCodeTestCase
+from aoc2024.src.day11.python.solution import count_stones
+
+
+class TestDay09Solution(AdventOfCodeTestCase):
+  def __init__(self, *args, **kwargs):
+    (super(TestDay09Solution, self).__init__(__file__, read_raw=True, *args,
+                                             **kwargs))
+
+  def test_part1_withOneBlink_counts(self):
+    self.assertEqual(7, count_stones(initial_state='0 1 10 99 999', blinks=1))
+
+  def test_part1_withMoreBlinks_counts(self):
+    initial_state = '125 17'
+    self.assertEqual(22, count_stones(initial_state, blinks=6))
+    self.assertEqual(55312, count_stones(initial_state, blinks=25))
+
+  def test_part1_withPuzzleInput_counts(self):
+    self.assertEqual(203457, count_stones(
+        initial_state='1 24596 0 740994 60 803 8918 9405859',
+        blinks=25))
+
+
+if __name__ == '__main__':
+  unittest.main()