Add code to solve part 2 of day 11

Author: r-sharp

2020/day_11/Python/seats.py

@@ -39,7 +39,6 @@ def get_adjacent_seats(seat_layout, seat_location):
     return adjacent_seats
 
 
-# Add apply rules for part2
 # new function for get_visible_seats
 def get_visible_seats(seat_layout, seat_location):
     """
@@ -48,31 +47,52 @@ def get_visible_seats(seat_layout, seat_location):
     and raster order.
 
     """
-    seat_location_x, seat_location_y = seat_location
+    seat_location_y, seat_location_x = seat_location
 
     # find visible seats by loop
     visible_seats = ['.', '.', '.', '.', '.', '.', '.', '.']
 
+    grid_size_x = len(seat_layout[0])
+    grid_size_y = len(seat_layout)
+
     for n in range(1, max(len(seat_layout), len(seat_layout[0])) + 1):
         # stop condition?
-        seat_x = max(seat_location_x - n, 0)
-        seat_y = max(seat_location_y - n, 0)
-
-        for x in range(seat_x, seat_location_x + n + 1, n):
-            for y in range(seat_y, seat_location_y + n + 1, n):
-                if (x != seat_location_x or y != seat_location_y): # don't count the seat we're on!!
-                    try:
+#        seat_x = max(seat_location_x - n, 0)
+#        seat_y = max(seat_location_y - n, 0)
+
+        # Direction index is COLUMN first. So NW is 0, W is 1, SW is 2 etc.
+        #   0    3   5
+        #
+        #   1  seat  6
+        #
+        #   2    4   7
+
+        direction_index = -1
+
+        for x in range(seat_location_x - n, seat_location_x + n + 1, n):
+            for y in range(seat_location_y -n, seat_location_y + n + 1, n):
+                # don't count the seat we're on!!
+                if (x != seat_location_x or y != seat_location_y):
+                    direction_index += 1
+                    if seat_is_in_grid(grid_size_x, grid_size_y, x, y):
+                    #try:
                         # only update visible seats if it's a floor
-                        direction_index = (n-1) % 8
                         if visible_seats[direction_index] == '.':
-                            visible_seats[direction_index] = seat_layout[x][y]
-                        print(f"where we are: {x, y} seat layout: {seat_layout[x][y]}")
-                    except IndexError:
-                        pass
+                            visible_seats[direction_index] = seat_layout[y][x]
+                    #except IndexError:
+                    #    pass
                 if '.' not in visible_seats:
                     return visible_seats
     return visible_seats
 
+def seat_is_in_grid(grid_size_x, grid_size_y, seat_location_x, seat_location_y):
+    '''returns true if seat is within the grid and False if it lies outside'''
+    result =  False
+    if (0 <= seat_location_x < grid_size_x):
+         if (0 <= seat_location_y < grid_size_y):
+             result = True
+
+    return result
 
 def apply_part1_rules(seat_layout):
     """
@@ -91,13 +111,33 @@ def apply_part1_rules(seat_layout):
                 new_seat = 'L'
             else:
                 new_seat = seat
-            #print(new_seat_layout[row_index])
             new_seat_layout[row_index][col_index] = new_seat
 
     return new_seat_layout
 
+# Add apply rules for part2
+def apply_part2_rules(seat_layout):
+    """
+    Apply rules once to the seat configuration.
+    """
+    new_seat_layout = copy.deepcopy(seat_layout)
+
+    for row_index, row in enumerate(seat_layout):
+
+        for col_index, seat in enumerate(row):
+            visible_seats = get_visible_seats(seat_layout, (row_index, col_index))
+            number_of_occupied_seats = visible_seats.count('#')
+            if seat == 'L' and number_of_occupied_seats == 0:
+                new_seat = '#'
+            elif seat == '#' and number_of_occupied_seats >= 5:
+                new_seat = 'L'
+            else:
+                new_seat = seat
+            new_seat_layout[row_index][col_index] = new_seat
+
+    return new_seat_layout
 
-def run(initial_seat_layout):
+def run_part1(initial_seat_layout):
     """
     Apply rules until the configuration reaches 'equilbrium' - applying the rules again changes nothing
     """
@@ -109,11 +149,29 @@ def run(initial_seat_layout):
         new_layout = apply_part1_rules(previous_layout)
     return new_layout
 
+def run_part2(initial_seat_layout):
+    """
+    Apply rules until the configuration reaches 'equilbrium' - applying the rules again changes nothing
+    """
+    # iterate apply rules until seat layout doesn't change
+    previous_layout = initial_seat_layout
+    new_layout = apply_part2_rules(initial_seat_layout)
+    count = 1
+    while new_layout != previous_layout:
+        previous_layout = new_layout
+        new_layout = apply_part2_rules(previous_layout)
+        print(f"looked at {count} layouts")
+        count += 1
+    return new_layout
+
 
 if __name__ == "__main__":
     # load initial seat layout and run
     initial_layout = loaders.load_string()
     initial_layout = process_puzzle_input(initial_layout)
-    final_layout = run(initial_layout)
+    final_layout = run_part1(initial_layout)
     number_of_seats = count_occupied_seats(final_layout)
     print(f'Part 1: {number_of_seats}')
+    final_layout = run_part2(initial_layout)
+    number_of_seats = count_occupied_seats(final_layout)
+    print(f'Part 2: {number_of_seats}')

2020/day_11/Python/test_seats.py

@@ -43,7 +43,7 @@ def test_get_adjacent_seats(seat_location, expected):
     "example_input,seat_location,expected",
     [
         [layouts.part2_example1, (4, 3), ["#", "#", "#", "#", "#", "#", "#", "#"]],
-        [layouts.part2_example2, (1, 1), [".", ".", "L", ".", ".", ".", ".", "."]],
+        [layouts.part2_example2, (1, 1), [".", ".", ".", ".", ".", ".", "L", "."]],
         [layouts.part2_example3, (3, 3), [".", ".", ".", ".", ".", ".", ".", "."]],
     ],
 )