Added solutions for day 12

askrepps · askrepps · commit dfd05ecb90aa · 2020-12-12T11:53:19.000-05:00
diff --git a/advent2020/day12.py b/advent2020/day12.py
@@ -0,0 +1,120 @@
+# MIT License
+#
+# Copyright (c) 2020 Andrew Krepps
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in all
+# copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+
+
+from . import util
+
+
+NORTH = (0, 1)
+SOUTH = (0, -1)
+EAST = (1, 0)
+WEST = (-1, 0)
+
+
+def parse_commands(lines):
+    return [(line[0], int(line[1:])) for line in lines]
+
+
+def move_forward(pos, direction, distance):
+    return pos[0] + direction[0]*distance, pos[1] + direction[1]*distance
+
+
+def move_ship(commands):
+    pos = (0, 0)
+    facings = [EAST, SOUTH, WEST, NORTH]
+    facing_idx = 0
+    for action, value in commands:
+        direction = (0, 0)
+        if action == 'N':
+            direction = NORTH
+        elif action == 'S':
+            direction = SOUTH
+        elif action == 'E':
+            direction = EAST
+        elif action == 'W':
+            direction = WEST
+        elif action == 'L':
+            assert value % 90 == 0
+            facing_idx = (facing_idx - value//90) % len(facings)
+        elif action == 'R':
+            assert value % 90 == 0
+            facing_idx = (facing_idx + value//90) % len(facings)
+        elif action == 'F':
+            direction = facings[facing_idx]
+        else:
+            raise ValueError(f"Unrecognized action: {action}")
+        pos = (pos[0] + direction[0]*value, pos[1] + direction[1]*value)
+    return pos
+
+
+def rotate_cw_90_deg(direction):
+    return direction[1], -direction[0]
+
+
+def move_ship_using_waypoint(commands, waypoint_pos):
+    ship_pos = (0, 0)
+    for action, value in commands:
+        waypoint_adj = (0, 0)
+        if action == 'N':
+            waypoint_adj = NORTH
+        elif action == 'S':
+            waypoint_adj = SOUTH
+        elif action == 'E':
+            waypoint_adj = EAST
+        elif action == 'W':
+            waypoint_adj = WEST
+        elif action == 'L':
+            assert value % 90 == 0
+            num_turns = (360 - value)//90
+            for _ in range(num_turns):
+                waypoint_pos = rotate_cw_90_deg(waypoint_pos)
+        elif action == 'R':
+            assert value % 90 == 0
+            num_turns = value//90
+            for _ in range(num_turns):
+                waypoint_pos = rotate_cw_90_deg(waypoint_pos)
+        elif action == 'F':
+            ship_pos = move_forward(ship_pos, waypoint_pos, value)
+        else:
+            raise ValueError(f"Unrecognized action: {action}")
+        waypoint_pos = move_forward(waypoint_pos, waypoint_adj, value)
+    return ship_pos
+
+
+def get_manhattan_distance_from_origin(pos):
+    return abs(pos[0]) + abs(pos[1])
+
+
+def get_part1_answer(commands):
+    return get_manhattan_distance_from_origin(move_ship(commands))
+
+
+def get_part2_answer(commands):
+    return get_manhattan_distance_from_origin(move_ship_using_waypoint(commands, (10, 1)))
+
+
+def run():
+    with open(util.get_input_file_path("day12.txt")) as f:
+        lines = [line.strip() for line in f if len(line.strip()) > 0]
+        commands = parse_commands(lines)
+        print(f"The answer to part 1 is {get_part1_answer(commands)}")
+        print(f"The answer to part 2 is {get_part2_answer(commands)}")
diff --git a/main.py b/main.py
@@ -34,6 +34,7 @@
 from advent2020 import day9
 from advent2020 import day10
 from advent2020 import day11
+from advent2020 import day12
 
 
 day_runners = [
@@ -47,7 +48,8 @@
     lambda: day8.run(),
     lambda: day9.run(),
     lambda: day10.run(),
-    lambda: day11.run()
+    lambda: day11.run(),
+    lambda: day12.run()
 ]
 
 
diff --git a/test/test_day12.py b/test/test_day12.py
@@ -0,0 +1,45 @@
+# MIT License
+#
+# Copyright (c) 2020 Andrew Krepps
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in all
+# copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+
+
+import unittest
+
+from advent2020.day12 import get_part1_answer
+from advent2020.day12 import get_part2_answer
+from advent2020.day12 import parse_commands
+
+
+ship_data = """
+F10
+N3
+F7
+R90
+F11
+"""
+
+
+class Day12Test(unittest.TestCase):
+    def test_day12(self):
+        lines = [line.strip() for line in ship_data.split("\n") if len(line.strip()) > 0]
+        commands = parse_commands(lines)
+        self.assertEqual(get_part1_answer(commands), 25)
+        self.assertEqual(get_part2_answer(commands), 286)
