c2971ee04e
Recently I've been asked a few interview questions that involve reading from or writing to a grid, matrix, game board, etc. I am not as fast as I'd like to be at this, so I'm going practice. Here I'm practicing reading from existing matrices. I should practice writing to empty boards, reading neigboring cells, wrapping around the board (in the case of Conway's Game of Life), and other useful practices.
59 lines
1.8 KiB
Python
59 lines
1.8 KiB
Python
# Herein I'm practicing two-dimensional matrix traversals in all directions of
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# which I can conceive:
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# 0. T -> B; L -> R
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# 1. T -> B; R -> L
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# 2. B -> T; L -> R
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# 3. B -> T; R -> L
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#
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# Commentary:
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# When I think of matrices, I'm reminded of cartesian planes. I think of the
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# cells as (X,Y) coordinates. This has been a pitfall for me because matrices
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# are usually encoded in the opposite way. That is, to access a cell at the
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# coordinates (X,Y) given a matrix M, you index M like this: M[Y][X]. To attempt
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# to avoid this confusion, instead of saying X and Y, I will prefer saying
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# "column" and "row".
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#
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# When traversing a matrix, you typically traverse vertically and then
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# horizontally; in other words, the rows come first followed by the columns. As
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# such, I'd like to refer to traversal orders as "top-to-bottom, left-to-right"
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# rather than "left-to-right, top-to-bottom".
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#
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# These practices are all in an attempt to rewire my thinking.
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# This is a list of matrices where the index of a matrix corresponds to the
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# order in which it should be traversed to produce the sequence:
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# [1,2,3,4,5,6,7,8,9].
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boards = [[[1, 2, 3], [4, 5, 6], [7, 8, 9]], [[3, 2, 1], [6, 5, 4], [9, 8, 7]],
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[[7, 8, 9], [4, 5, 6], [1, 2, 3]], [[9, 8, 7], [6, 5, 4], [3, 2, 1]]]
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# T -> B; L -> R
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board = boards[0]
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result = []
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for row in board:
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for col in row:
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result.append(col)
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print(result)
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# T -> B; R -> L
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board = boards[1]
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result = []
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for row in board:
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for col in reversed(row):
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result.append(col)
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print(result)
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# B -> T; L -> R
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board = boards[2]
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result = []
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for row in reversed(board):
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for col in row:
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result.append(col)
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print(result)
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# B -> T; R -> L
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board = boards[3]
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result = []
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for row in reversed(board):
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for col in reversed(row):
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result.append(col)
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print(result)
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