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problem11.py
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"""Solves Problem 11 from Project Euler."""
OFFSET = 3
GRID = [
[8, 2, 22, 97, 38, 15, 0, 40, 0, 75, 4, 5, 7, 78, 52, 12, 50, 77, 91, 8],
[49, 49, 99, 40, 17, 81, 18, 57, 60, 87, 17, 40, 98, 43, 69, 48, 4, 56, 62, 0],
[81, 49, 31, 73, 55, 79, 14, 29, 93, 71, 40, 67, 53, 88, 30, 3, 49, 13, 36, 65],
[52, 70, 95, 23, 4, 60, 11, 42, 69, 24, 68, 56, 1, 32, 56, 71, 37, 2, 36, 91],
[22, 31, 16, 71, 51, 67, 63, 89, 41, 92, 36, 54, 22, 40, 40, 28, 66, 33, 13, 80],
[24, 47, 32, 60, 99, 3, 45, 2, 44, 75, 33, 53, 78, 36, 84, 20, 35, 17, 12, 50],
[32, 98, 81, 28, 64, 23, 67, 10, 26, 38, 40, 67, 59, 54, 70, 66, 18, 38, 64, 70],
[67, 26, 20, 68, 2, 62, 12, 20, 95, 63, 94, 39, 63, 8, 40, 91, 66, 49, 94, 21],
[24, 55, 58, 5, 66, 73, 99, 26, 97, 17, 78, 78, 96, 83, 14, 88, 34, 89, 63, 72],
[21, 36, 23, 9, 75, 0, 76, 44, 20, 45, 35, 14, 0, 61, 33, 97, 34, 31, 33, 95],
[78, 17, 53, 28, 22, 75, 31, 67, 15, 94, 3, 80, 4, 62, 16, 14, 9, 53, 56, 92],
[16, 39, 5, 42, 96, 35, 31, 47, 55, 58, 88, 24, 0, 17, 54, 24, 36, 29, 85, 57],
[86, 56, 0, 48, 35, 71, 89, 7, 5, 44, 44, 37, 44, 60, 21, 58, 51, 54, 17, 58],
[19, 80, 81, 68, 5, 94, 47, 69, 28, 73, 92, 13, 86, 52, 17, 77, 4, 89, 55, 40],
[4, 52, 8, 83, 97, 35, 99, 16, 7, 97, 57, 32, 16, 26, 26, 79, 33, 27, 98, 66],
[88, 36, 68, 87, 57, 62, 20, 72, 3, 46, 33, 67, 46, 55, 12, 32, 63, 93, 53, 69],
[4, 42, 16, 73, 38, 25, 39, 11, 24, 94, 72, 18, 8, 46, 29, 32, 40, 62, 76, 36],
[20, 69, 36, 41, 72, 30, 23, 88, 34, 62, 99, 69, 82, 67, 59, 85, 74, 4, 36, 16],
[20, 73, 35, 29, 78, 31, 90, 1, 74, 31, 49, 71, 48, 86, 81, 16, 23, 57, 5, 54],
[1, 70, 54, 71, 83, 51, 54, 69, 16, 92, 33, 48, 61, 43, 52, 1, 89, 19, 67, 48]
]
INVALID_COORDS_PRODUCT = 0
def _calc_up(row_index, col_index):
"""Build the sequence going straight up from row_index."""
if row_index < OFFSET:
return INVALID_COORDS_PRODUCT
return GRID[row_index][col_index] * \
GRID[row_index - 1][col_index] * \
GRID[row_index - 2][col_index] * \
GRID[row_index - 3][col_index]
def _calc_down(row_index, col_index):
"""Build the sequence going straight down from row_index."""
if row_index + OFFSET >= len(GRID):
return INVALID_COORDS_PRODUCT
return GRID[row_index][col_index] * \
GRID[row_index + 1][col_index] * \
GRID[row_index + 2][col_index] * \
GRID[row_index + 3][col_index]
def _calc_left(row_index, col_index):
"""Build the sequence going straight left from col_index."""
if col_index < OFFSET:
return INVALID_COORDS_PRODUCT
return GRID[row_index][col_index] * \
GRID[row_index][col_index - 1] * \
GRID[row_index][col_index - 2] * \
GRID[row_index][col_index - 3]
def _calc_right(row_index, col_index):
"""Build the sequence going straight right from row_index."""
if col_index + OFFSET >= len(GRID[row_index]):
return INVALID_COORDS_PRODUCT
return GRID[row_index][col_index] * \
GRID[row_index][col_index + 1] * \
GRID[row_index][col_index + 2] * \
GRID[row_index][col_index + 3]
def _calc_up_right(row_index, col_index):
"""Build the sequence going up and to the right from \
(row_index, col_index)."""
if row_index < OFFSET:
return INVALID_COORDS_PRODUCT
if col_index + OFFSET >= len(GRID[row_index]):
return INVALID_COORDS_PRODUCT
return GRID[row_index][col_index] * \
GRID[row_index - 1][col_index + 1] * \
GRID[row_index - 2][col_index + 2] * \
GRID[row_index - 3][col_index + 3]
def _calc_down_right(row_index, col_index):
"""Build the sequence going down and to the right from \
(row_index, col_index)."""
if row_index + OFFSET >= len(GRID):
return INVALID_COORDS_PRODUCT
if col_index + OFFSET >= len(GRID[row_index]):
return INVALID_COORDS_PRODUCT
return GRID[row_index][col_index] * \
GRID[row_index + 1][col_index + 1] * \
GRID[row_index + 2][col_index + 2] * \
GRID[row_index + 3][col_index + 3]
def _calc_down_left(row_index, col_index):
"""Build the sequence going down and to the left from \
(row_index, col_index)."""
if row_index + OFFSET >= len(GRID):
return INVALID_COORDS_PRODUCT
if col_index < OFFSET:
return INVALID_COORDS_PRODUCT
return GRID[row_index][col_index] * \
GRID[row_index + 1][col_index - 1] * \
GRID[row_index + 2][col_index - 2] * \
GRID[row_index + 3][col_index - 3]
def _calc_up_left(row_index, col_index):
"""Build the sequence going down and to the left from \
(row_index, col_index)."""
if row_index < OFFSET:
return INVALID_COORDS_PRODUCT
if col_index < OFFSET:
return INVALID_COORDS_PRODUCT
return GRID[row_index][col_index] * \
GRID[row_index - 1][col_index - 1] * \
GRID[row_index - 2][col_index - 2] * \
GRID[row_index - 3][col_index - 3]
def _calc_all_possible_sequences():
"""Build a set of all possible 4-element sequences."""
products = set()
for row in range(len(GRID)):
for col in range(len(GRID[row])):
products.add(_calc_up(row, col))
products.add(_calc_down(row, col))
products.add(_calc_left(row, col))
products.add(_calc_right(row, col))
products.add(_calc_up_right(row, col))
products.add(_calc_down_right(row, col))
products.add(_calc_down_left(row, col))
products.add(_calc_up_left(row, col))
return products
def problem_11():
"""Find the largest product of four adjacent elements."""
return max(_calc_all_possible_sequences())
if __name__ == '__main__':
print problem_11()