Problem with rotating a two-dimensional array in python

Question

How to to make this array rotate by 90 degrees to right without using numpy.

multiarray = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
auxiliaryArray = []
colLength = len(multiarray[0])
rowLength = len(multiarray)
for indexRow in range(len(multiarray)):
    for indexCol in range(len(multiarray[0])):
        auxiliaryArray[indexCol][rowLength - 1 - indexRow] = multiarray[indexRow][indexCol]

print(auxiliaryArray)

Error: IndexError: list index out of range

Desired Output: [[7, 4, 1], [8, 5, 2], [9, 6, 3]]

instead of making an empty `list`, initialize a `list` with zeroes or some other values, that way you can't get out of range error — Mahrkeenerh, Nov 04 '21 at 16:49
if you are looking at mathematic way without using additional library you can read this. https://integratedmlai.com/matrixinverse/ — Shahin Shirazi, Nov 04 '21 at 16:53

score 0 · Accepted Answer · answered Nov 04 '21 at 16:49

0

You can use zip on the reversed array:

auxiliaryArray = list(zip(*multiarray[::-1]))

or

auxiliaryArray = list(zip(*reversed(multiarray)))

output: [(7, 4, 1), (8, 5, 2), (9, 6, 3)]

If you need lists and not tuples:

auxiliaryArray = list(map(list, zip(*reversed(multiarray))))

output: [[7, 4, 1], [8, 5, 2], [9, 6, 3]]

answered Nov 04 '21 at 16:49

mozway

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Could it be done with append? – Zukashi Nov 04 '21 at 16:59
Why? Is this an assignment? – mozway Nov 04 '21 at 17:02
Something like that – Zukashi Nov 04 '21 at 17:03
1

I take this as a yes… Yes it can be done, but you should have made it explicit from the beginning that it was an assignment (cf. SO guidelines), your question wouldn't have been closed – mozway Nov 04 '21 at 17:06

score 0 · Answer 2 · answered Nov 04 '21 at 16:50

0

This does it:

list(zip(*multiarray[::-1]))

answered Nov 04 '21 at 16:50

Serge de Gosson de Varennes

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Problem with rotating a two-dimensional array in python

2 Answers2