Instagram Engineering Challenge

image.png

insta.rb

#!/usr/bin/env ruby

require 'RMagick'
include Magick

#Match right edge of col1 to left edge of col2
def match_edge(col1, col2)
  left_edge            = col2.get_pixels(0,0,1,col2.rows)
  left_edge_plus_one   = col2.get_pixels(1,0,1,col2.rows)
  right_edge           = col1.get_pixels(col1.columns - 2,0,1,col1.rows)
  right_edge_minus_one = col1.get_pixels(col1.columns - 3,0,1,col1.rows)

  score = 0

  col1.rows.times { |i|
    tmp = 0
    difference = (left_edge[i].red - left_edge_plus_one[i].red).abs
    if((right_edge[i].red - left_edge[i].red).abs <= difference)
      tmp += 1
    end

    difference = (left_edge[i].blue - left_edge_plus_one[i].blue).abs
    if((right_edge[i].blue - left_edge[i].blue).abs <= difference)
      tmp += 1
    end

    difference = (left_edge[i].green - left_edge_plus_one[i].green).abs
    if((right_edge[i].green - left_edge[i].green).abs <= difference)
      tmp += 1
    end
    if tmp > 1
      score += 1
    end
  }
  score
end

cols = []
img = ImageList.new("image.png")

#Divide into columns
20.times { |index|
  cols.push img.excerpt(index*32,0,32,img.rows)
}

#Find leftmost edge
cols.each_with_index { |col1, i|
  flag = false
  cols.each_with_index { |col2, j|
    if i != j
      if match_edge(col2, col1) > 100
        flag = true
      end
    end
  }
  if not flag
    tmp = cols[0]
    cols[0] = cols[i]
    cols[i] = tmp
  end
}

#Find matching edges for other columns
cols.length.times { |i|
  if(i < cols.size - 1)
    max_match = 0
    max_index = 0
    cols.length.times { |j|
      if(i < j)
        match = match_edge(cols[i], cols[j])
        if match >= max_match
          max_match = match
          max_index = j
        end
      end
    }
    #puts "Moving #{max_index} to #{i+1}"
    tmp = cols[i+1]
    cols[i+1] = cols[max_index]
    cols[max_index] = tmp
  end
}

il = ImageList.new
cols.each { |col| 
  il << col
}
il.append(false).write("output.png")

output.png