Ruby - rotateArrayMatrix.txt

Write a rotate function that rotates a two-dimensional array (a matrix) either clockwise or anti-clockwise by 90 degrees, and returns the rotated array.

The function accepts two parameters: an array, and a string specifying the direction or rotation. The direction will be either "clockwise" or "counter-clockwise".


- - - - - - - my answer (updated for non-square matrix) - - - - - - -


def rotate matrix, direction
    newMatrix, finalMatrix, i = [], [], 0
    (matrix.length > matrix[0].length ? matrix.length : matrix[0].length).times do
        matrix.map { |row| row[i] != nil ? newMatrix << row[i] : nil }
        i+=1
    end
    direction == 'clockwise' ? newMatrix.each_slice(matrix.length).to_a.map { |newRow| newRow.reverse} : newMatrix.each_slice(matrix.length).to_a.reverse
end


- start with initializing two empty arrays and an index-counter
- a number of times (which ever is bigger (columns or rows)), do the following:
  - each pass through will only look at index ‘0’ or ‘1’ or ‘2’ ... etc pushing those items in sequentially.
  - if the value does not equal ‘nil’ (which would occur because the matrix had more rows than columns), push the value into newMatrix.
- increment ‘i’ up one with each complete pass.

^^^ (this has the function of switching ‘rows’ with ‘columns’) ^^^

- if direction was ‘clockwise’ the answer array needs to be broken up into the original size rows (using ‘.each_slice’)
  - then reverse each row-array to correctly position each element
- else if direction was ‘counter-clockwise’ we reverse the position of each row.





- - - alt - - -

def rotate matrix, direction
  case direction
  when 'clockwise'
    matrix.transpose.map(&:reverse)
  when 'counter-clockwise'
    matrix.transpose.reverse
  end
end


- - - alt - - -

def rotate matrix, direction
  direction == "clockwise" ? matrix.transpose.map {|e| e.reverse} : matrix.transpose.reverse
end


- ‘.transpose’ takes in an array of arrays and swaps the rows and columns. essentially the top 4 lines of my code.
  - then reverse either the columns within each row
  - or the order of whole rows
- done and done