day08: coverage

day08/day8.py

@@ -2,6 +2,7 @@
 import itertools
 import math
 from dataclasses import dataclass, field
+from typing import Iterator
 
 INPUT = "day08/input.txt"
 INPUT_A = "day08/input-a.txt"
@@ -56,6 +57,10 @@ class Directions:
     def get_step(self, index: int) -> str:
         return self.steps[index % len(self.steps)]
 
+    def get_steps_iterator(self) -> Iterator[str]:
+        """Returns a iterator that loops through indefinitely."""
+        return itertools.cycle(self.steps)
+
 
 @dataclass
 class Cycle:
@@ -87,10 +92,9 @@ def get_location(self, index: int) -> LocationStep:
 
         # 2nd half of array is from cycle_start_index -> end
         index -= len(self.location_steps)
-        index %= self.cycle_length
         index += self.cycle_start_index
-        if index >= len(self.location_steps):
-            raise ValueError("you fucked up")
+        index %= self.cycle_length
+
         return self.location_steps[index]
 
 
@@ -117,7 +121,7 @@ def follow_directions(directions: Directions, world_map: WorldMap) -> int:
     mappings = world_map.mappings
     node: Location = mappings["AAA"]
     nodes_visited = 0
-    for step in itertools.cycle(directions.steps):
+    for step in directions.get_steps_iterator():
         if step == "L":
             node = mappings[node.left]
         else:
@@ -126,7 +130,7 @@ def follow_directions(directions: Directions, world_map: WorldMap) -> int:
         if node.name == "ZZZ":
             return nodes_visited
 
-    return -1
+    raise AssertionError("Unreachable; iterator is infinite")
 
 
 def get_location_as(world_map: WorldMap) -> list[Location]:

day08/tests/test_day8.py

@@ -3,6 +3,7 @@
     INPUT_B,
     INPUT_C,
     Cycle,
+    Directions,
     Location,
     find_cycle,
     follow_directions,
@@ -43,3 +44,9 @@ def test_find_cycle() -> None:
     cycle_22A: Cycle = find_cycle(location_22A, world_map, directions)
     assert cycle_11A.cycle_length == 2
     assert cycle_22A.cycle_length == 6
+
+
+def test_directions() -> None:
+    directions: Directions = Directions("LRLRLLR")
+    assert directions.get_step(0) == "L"
+    assert directions.get_step(7) == "L"

pyproject.toml

@@ -33,7 +33,12 @@ relative_files = true
 
 
 [tool.coverage.report]
-exclude_lines = ["if __name__ == .__main__.:", "def main", "if TYPE_CHECKING:"]
+exclude_lines = [
+    "if __name__ == .__main__.:",
+    "def main",
+    "if TYPE_CHECKING:",
+    "raise AssertionError",
+]
 omit = ["download_inputs.py", "maker.py"]
 precision = 2
 skip_covered = true