TheAlgorithms-Python

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"""
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What is the greatest product of four adjacent numbers (horizontally,
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vertically, or diagonally) in this 20x20 array?
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08 02 22 97 38 15 00 40 00 75 04 05 07 78 52 12 50 77 91 08
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49 49 99 40 17 81 18 57 60 87 17 40 98 43 69 48 04 56 62 00
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81 49 31 73 55 79 14 29 93 71 40 67 53 88 30 03 49 13 36 65
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52 70 95 23 04 60 11 42 69 24 68 56 01 32 56 71 37 02 36 91
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22 31 16 71 51 67 63 89 41 92 36 54 22 40 40 28 66 33 13 80
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24 47 32 60 99 03 45 02 44 75 33 53 78 36 84 20 35 17 12 50
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32 98 81 28 64 23 67 10 26 38 40 67 59 54 70 66 18 38 64 70
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67 26 20 68 02 62 12 20 95 63 94 39 63 08 40 91 66 49 94 21
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24 55 58 05 66 73 99 26 97 17 78 78 96 83 14 88 34 89 63 72
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21 36 23 09 75 00 76 44 20 45 35 14 00 61 33 97 34 31 33 95
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78 17 53 28 22 75 31 67 15 94 03 80 04 62 16 14 09 53 56 92
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16 39 05 42 96 35 31 47 55 58 88 24 00 17 54 24 36 29 85 57
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86 56 00 48 35 71 89 07 05 44 44 37 44 60 21 58 51 54 17 58
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19 80 81 68 05 94 47 69 28 73 92 13 86 52 17 77 04 89 55 40
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04 52 08 83 97 35 99 16 07 97 57 32 16 26 26 79 33 27 98 66
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88 36 68 87 57 62 20 72 03 46 33 67 46 55 12 32 63 93 53 69
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04 42 16 73 38 25 39 11 24 94 72 18 08 46 29 32 40 62 76 36
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20 69 36 41 72 30 23 88 34 62 99 69 82 67 59 85 74 04 36 16
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20 73 35 29 78 31 90 01 74 31 49 71 48 86 81 16 23 57 05 54
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01 70 54 71 83 51 54 69 16 92 33 48 61 43 52 01 89 19 67 48
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"""
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import os
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def largest_product(grid):
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    n_columns = len(grid[0])
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    n_rows = len(grid)
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    largest = 0
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    lr_diag_product = 0
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    rl_diag_product = 0
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    # Check vertically, horizontally, diagonally at the same time (only works
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    # for nxn grid)
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    for i in range(n_columns):
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        for j in range(n_rows - 3):
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            vert_product = grid[j][i] * grid[j + 1][i] * grid[j + 2][i] * grid[j + 3][i]
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            horz_product = grid[i][j] * grid[i][j + 1] * grid[i][j + 2] * grid[i][j + 3]
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            # Left-to-right diagonal (\) product
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            if i < n_columns - 3:
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                lr_diag_product = (
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                    grid[i][j]
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                    * grid[i + 1][j + 1]
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                    * grid[i + 2][j + 2]
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                    * grid[i + 3][j + 3]
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                )
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            # Right-to-left diagonal(/) product
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            if i > 2:
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                rl_diag_product = (
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                    grid[i][j]
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                    * grid[i - 1][j + 1]
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                    * grid[i - 2][j + 2]
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                    * grid[i - 3][j + 3]
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                )
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            max_product = max(
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                vert_product, horz_product, lr_diag_product, rl_diag_product
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            )
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            if max_product > largest:
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                largest = max_product
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    return largest
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def solution():
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    """Returns the greatest product of four adjacent numbers (horizontally,
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    vertically, or diagonally).
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    >>> solution()
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    70600674
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    """
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    grid = []
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    with open(os.path.dirname(__file__) + "/grid.txt") as file:
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        for line in file:
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            grid.append(line.strip("\n").split(" "))
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    grid = [[int(i) for i in grid[j]] for j in range(len(grid))]
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    return largest_product(grid)
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if __name__ == "__main__":
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    print(solution())
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