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https://github.com/thib8956/advent-of-code.git
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73 lines
2.2 KiB
Python
73 lines
2.2 KiB
Python
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DIRECTIONS = (
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(0, -1), # N
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(-1, -1), # NW
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(1, -1), # NE
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(-1, 0), # W
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(1, 0), # E
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(0, 1), # S
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(-1, 1), # SW
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(1, 1), # SE
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)
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def get_grid_pos(grid, pos):
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x, y = pos
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if 0 <= x < len(grid):
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if 0 <= y < len(grid[0]):
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return grid[y][x]
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return None
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def part1(grid):
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count = 0
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for y, row in enumerate(grid):
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for x, letter in enumerate(row):
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if letter != "X":
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continue
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for direction in DIRECTIONS:
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acc = letter
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for i in range(1, 4):
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dx, dy = direction
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pos = (x + i*dx, y + i*dy)
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next_letter = get_grid_pos(grid, pos)
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if next_letter is not None:
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acc += next_letter
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else:
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break # out-of-bounds, go to next direction
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if acc == "XMAS":
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count += 1
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print("Part 1: ", count)
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def part2(grid):
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count = 0
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for y, row in enumerate(grid):
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for x, _ in enumerate(row):
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if y + 2 >= len(grid) or x + 2 >= len(grid[0]):
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continue
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if grid[y+1][x+1] != "A": # center letter is always "A"
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continue
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# M.S / .A. / M.S
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if grid[y][x] == "M" and grid[y][x+2] == "S" and grid[y+2][x] == "M" and grid[y+2][x+2] == "S":
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count += 1
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# M.M / .A. / S.S
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if grid[y][x] == "M" and grid[y][x+2] == "M" and grid[y+2][x] == "S" and grid[y+2][x+2] == "S":
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count += 1
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# S.M / .A. / S.M
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if grid[y][x] == "S" and grid[y][x+2] == "M" and grid[y+2][x] == "S" and grid[y+2][x+2] == "M":
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count += 1
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# S.S / .A. / M.M
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if grid[y][x] == "S" and grid[y][x+2] == "S" and grid[y+2][x] == "M" and grid[y+2][x+2] == "M":
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count += 1
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print("Part 2: ", count)
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if __name__ == "__main__":
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import sys
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infile = sys.argv[1] if 1 < len(sys.argv) else "example.txt"
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with open(infile) as f:
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grid = [l.rstrip() for l in f.readlines()]
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part1(grid)
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part2(grid)
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