My Advent of Code solutions in Python.
kevinyap.ca/2019/12/going-fast-in-advent-of-code/
advent-of-code
python
Add solution for 2023/14
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2023/day14.py
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2023/day14.py
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import copy
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import fileinput
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from utils import Point, N, S, E, W
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# Parse problem input.
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BOARD = {}
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for y, line in enumerate(fileinput.input()):
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for x, c in enumerate(line.strip()):
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BOARD[Point(x, y)] = c
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WIDTH = x + 1
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HEIGHT = y + 1
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def tilt(board, direction):
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if direction == N:
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for y in range(1, HEIGHT):
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for x in range(WIDTH):
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p = Point(x, y)
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if board[p] != 'O':
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continue
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while p.y > 0:
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np = p + S
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if board[np] == '.':
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board[p] = '.'
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board[np] = 'O'
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else:
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break
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p = np
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elif direction == S:
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for y in reversed(range(HEIGHT - 1)):
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for x in range(WIDTH):
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p = Point(x, y)
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if board[p] != 'O':
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continue
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while p.y < HEIGHT - 1:
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np = p + N
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if board[np] == '.':
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board[p] = '.'
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board[np] = 'O'
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else:
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break
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p = np
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elif direction == E:
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for x in reversed(range(WIDTH)):
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for y in range(HEIGHT):
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p = Point(x, y)
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if board[p] != 'O':
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continue
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while p.x < WIDTH - 1:
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np = p + E
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if board[np] == '.':
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board[p] = '.'
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board[np] = 'O'
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else:
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break
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p = np
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elif direction == W:
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for x in range(1, WIDTH):
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for y in range(HEIGHT):
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p = Point(x, y)
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if board[p] != 'O':
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continue
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while p.x > 0:
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np = p + W
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if board[np] == '.':
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board[p] = '.'
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board[np] = 'O'
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else:
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break
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p = np
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def spin_cycle(board):
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for x in [N, W, S, E]:
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tilt(board, x)
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def total_load(board):
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return sum(HEIGHT - p.y for p, c in board.items() if c == 'O')
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def serialize(board):
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s = ''
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for y in range(HEIGHT):
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for x in range(WIDTH):
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s += board[Point(x, y)]
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return s
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# Solve part 1.
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part_1_board = copy.deepcopy(BOARD)
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tilt(part_1_board, N)
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print("Part 1:", total_load(part_1_board))
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# Detect cycle length.
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board_states = {}
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c = 1
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while True:
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spin_cycle(BOARD)
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s = serialize(BOARD)
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if s in board_states:
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cycle_len = c - board_states[s]
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print(f"Determined period = {cycle_len} on iteration {c}.")
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break
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else:
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board_states[s] = c
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c += 1
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# Simulate further ahead to work out part 2 answer.
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while c % cycle_len != 1000000000 % cycle_len:
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spin_cycle(BOARD)
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c += 1
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print("Part 2:", total_load(BOARD))
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