Matrix Rotation of elements - Algorithms
12-15-2019, 06:16 AM (This post was last modified: 12-16-2019 12:54 PM by Ángel Martin.)
Post: #4
 Ángel Martin Senior Member Posts: 1,319 Joined: Dec 2013
RE: Matrix Rotation of elements - Algorithms
here's a start, surely not the best approach but it seems to do the job:

for an (m x n) matrix, the rotated matrix (one single step, clockwise) bij is given as follows:-

FOR k = 0 TO int(m/2)-1 ; current layer

FOR j = k+1 TO (n-1-k) ; top row rightwards
b(1+k),(j+1) = a(1+k),j
NEXT j

FOR i = (1+k) TO (m-1-k) ; rightmost column downwards
b(i+1),(n-k) = a i,(n-k)
NEXT i

FOR j = (n-k) TO (2+k) STEP -1 ; bottom row leftwards
b(m-k),(j-1) = a(m-k),j
NEXT j

FOR i = (m-k) TO (2+k) STEP -1 ; leftfmost column upwards
b(i-1),(1+k) = a i,(1+k)
NEXT i

NEXT k ; next layer

Edited: corrected typos in indexes
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 Messages In This Thread Matrix Rotation of elements - Algorithms - Ángel Martin - 12-12-2019, 02:37 PM RE: Matrix Rotation of elements - Algorithms - Csaba Tizedes - 12-12-2019, 03:31 PM RE: Matrix Rotation of elements - Algorithms - Ángel Martin - 12-12-2019, 03:59 PM RE: Matrix Rotation of elements - Algorithms - Ángel Martin - 12-15-2019 06:16 AM RE: Matrix Rotation of elements - Algorithms - Ángel Martin - 12-17-2019, 10:46 AM RE: Matrix Rotation of elements - Algorithms - Valentin Albillo - 12-17-2019, 04:18 PM RE: Matrix Rotation of elements - Algorithms - Ángel Martin - 12-18-2019, 06:29 AM RE: Matrix Rotation of elements - Algorithms - Csaba Tizedes - 12-17-2019, 02:22 PM RE: Matrix Rotation of elements - Algorithms - Ángel Martin - 12-17-2019, 03:51 PM RE: Matrix Rotation of elements - Algorithms - Paul Dale - 12-18-2019, 07:05 AM

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