spiral_traversal_matrix.rb

# Print a given matrix in spiral form
# Input:  1    2   3   4
#         5    6   7   8
#         9   10  11  12
#         13  14  15  16
# Output: 1 2 3 4 8 12 16 15 14 13 9 5 6 7 11 10
# Explanation: The output is matrix in spiral format.

# a = [[1, 2, 3, 4, 5, 6],
#      [7, 8, 9, 10, 11, 12],
#      [13, 14, 15, 16, 17, 18]]

#  output    1 2 3 4 5 6 12 18 17 16 15 14 13 7 8 9 10 11

def spiral_traversal(ar)
  result = []
  rows = ar.length
  cols = ar[0].length

  left = 0
  right = cols - 1
  top = 0
  bottom = rows - 1

  while left <= right && top <= bottom
    (left..right).each do |j|
      result.append ar[left][j]
    end

    ((left + 1)..bottom).each do |i|
      result.append ar[i][right]
    end

    if top < bottom && left < right
      (right - 1).downto(left + 1).each do |j|
        result.append ar[bottom][j]
      end
    end

    if left < right && left < right
      (bottom - 1).downto(top + 1).each do |i|
        result.append ar[i][left]
      end
    end

    left += 1
    right -= 1
    top += 1
    bottom -= 1
  end
  puts result
end

arr = [[1, 2, 3, 4],
       [5, 6, 7, 8],
       [9, 10, 11, 12],
       [13, 14, 15, 16]]

# spiral_traversal(arr)

arr = [[1, 2, 3, 4, 5, 6],
       [7, 8, 9, 10, 11, 12],
       [13, 14, 15, 16, 17, 18]]

spiral_traversal(arr)