Day 16

Author: davidaugustat

day16/day16.py

@@ -0,0 +1,107 @@
+def get_next_directions(tile, current_direction):
+ if tile == '.':
+ return [current_direction]
+ 
+ if tile == "/":
+ if current_direction == "l":
+ return ["d"]
+ if current_direction == "r":
+ return ["u"]
+ if current_direction == "u":
+ return ["r"]
+ if current_direction == "d":
+ return ["l"]
+ 
+ if tile == "\\":
+ if current_direction == "l":
+ return ["u"]
+ if current_direction == "r":
+ return ["d"]
+ if current_direction == "u":
+ return ["l"]
+ if current_direction == "d":
+ return ["r"]
+ 
+ if tile == "|":
+ if current_direction in "ud":
+ return [current_direction]
+ return ["u", "d"]
+ 
+ if tile == "-":
+ if current_direction in "lr":
+ return [current_direction]
+ return ["l", "r"]
+ 
+ raise Exception("Invalid tile!")
+
+
+def get_next_tile(i, j, dir, grid):
+ if dir == "l":
+ i_next, j_next = i, j-1
+ if dir == "r":
+ i_next, j_next = i, j+1
+ if dir == "u":
+ i_next, j_next = i-1, j
+ if dir == "d":
+ i_next, j_next = i+1, j
+ 
+ if i_next < 0 or i_next >= len(grid) or j_next < 0 or j_next >= len(grid[0]):
+ return None, None
+ return i_next, j_next
+
+
+def trace_light(grid, start_i, start_j, start_dir):
+ r = len(grid)
+ c = len(grid[0])
+
+ energized_count = 0
+ energized = [[False for _ in range(c)] for _ in range(r)]
+ dirs_applied_to_tile = [[[] for _ in range(c)] for _ in range(r)]
+
+ to_process = [(start_i, start_j, start_dir)]
+ while len(to_process) > 0:
+ i, j, dir = to_process.pop()
+ if not energized[i][j]:
+ energized[i][j] = True
+ energized_count += 1
+ if dir not in dirs_applied_to_tile[i][j]:
+ dirs_applied_to_tile[i][j].append(dir)
+
+ next_dirs = get_next_directions(grid[i][j], dir)
+ for next_dir in next_dirs:
+ i_next, j_next = get_next_tile(i, j, next_dir, grid)
+ if i_next != None and next_dir not in dirs_applied_to_tile[i_next][j_next]:
+ to_process.append((i_next, j_next, next_dir))
+ 
+ return energized_count
+
+
+def part1(grid):
+ energized_count = trace_light(grid, 0, 0, "r")
+ print("Part 1 Result:", energized_count)
+
+
+def part2(grid):
+ r = len(grid)
+ c = len(grid[0])
+
+ max_top_row = max(trace_light(grid, 0, j, "d") for j in range(c))
+ max_bottom_row = max(trace_light(grid, r-1, j, "u") for j in range(c))
+ max_left_row = max(trace_light(grid, i, 0, "r") for i in range(r))
+ max_right_row = max(trace_light(grid, i, c-1, "l") for i in range(r))
+
+ max_energized = max(max_top_row, max_bottom_row, max_left_row, max_right_row)
+ print("Part 2 Result:", max_energized)
+ 
+
+def read_data_from_file(filename):
+ with open(filename) as file:
+ grid = [line.rstrip() for line in file]
+ return grid
+
+
+grid = read_data_from_file("input.txt")
+# grid = read_data_from_file("testinput.txt")
+
+part1(grid)
+part2(grid)