79 lines
2.5 KiB
Python
79 lines
2.5 KiB
Python
def num_neighbours(lines: [], line_index: int, pos_index: int, num_lines: int, line_length: int) -> int:
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'''Check surrounding and current row neighbours of a given position.
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Does not operate on 2d coords directly, but on index and current versus prev/next lines.
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'''
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total = 0
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for ii in range(max(0, line_index - 1), min(num_lines, line_index + 2)):
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for jj in range(max(0, pos_index - 1), min(line_length, pos_index + 2)):
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if ii == line_index and jj == pos_index:
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continue
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if lines[ii][jj] == '@':
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total += 1
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return total
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def process_line(lines: []) -> int:
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'''Iterate through all lines in the map and determine which can be removed this time around'''
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total = 0
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for line_index, line in enumerate(lines):
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for index, char in enumerate(line):
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if char == '@':
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total_neighbours = num_neighbours(lines, line_index, index, len(lines), len(line))
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if total_neighbours < 4:
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total += 1
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return total
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def find_all_accessible_rolls(lines: []) -> int:
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'''Recursively iterate through removing paper rolls and see how many are opened up for removal after each pass until none can be removed'''
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total = 0
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# Copy the map to note which have been removed without affecting the current checks
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lines_copy = lines
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for line_index, line in enumerate(lines):
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for index, char in enumerate(line):
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if char == '@':
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total_neighbours = 0
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for ii in range(max(0, line_index - 1), min(len(lines), line_index + 2)):
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for jj in range(max(0, index - 1), min(len(line), index + 2)):
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if ii == line_index and jj == index:
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continue
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if lines[ii][jj] == '@':
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total_neighbours += 1
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if total_neighbours < 4:
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total += 1
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temp_line = list(lines_copy[line_index])
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temp_line[index] = '.'
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lines_copy[line_index] = ''.join(temp_line)
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if total != 0:
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return total + find_all_accessible_rolls(lines_copy)
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return total
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def main():
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'''Entrypoint'''
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with open('input.txt', encoding='utf-8') as fh:
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all_lines = fh.readlines()
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part1_total = process_line(all_lines)
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print(f'Part 1: {part1_total}')
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part2_total = find_all_accessible_rolls(all_lines)
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print(f'Part 2: {part2_total}')
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if __name__ == "__main__":
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main()
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