[Ruby] 二次元配列を列方向に足し合わせる（長さが異なる配列も可） ref: http://qiita.com/kidachi_/items/0e8b065b37d94c9c2362

file0.txt

# [[1,1,1],[2,3],[4]] の場合、

[1, 1 ,1]
[2, 3    ]
[4        ]
 ↓↓↓ 列（タテ）方向に足し合わせる
[7, 4, 1]

file1.txt

# [1,1,1],[2,3,4] のinputで、[3,4,5] のoutputが欲しい
[13] pry(main)> [[1,1,1],[2,3,4]].transpose.map{|ary| ary.inject(&:+)}
=> [3, 4, 5]

file2.txt

# [1,1,1],[2,3],[4] のinputで、[7,4,1] のoutputが欲しい
[14] pry(main)> [[1,1,1],[2,3],[4]].transpose.map{|ary| ary.inject(&:+)}
IndexError: element size differs (2 should be 3)

file3.txt

[42] pry(main)> array = [[1,1,1],[2,3],[4]]
=> [[1, 1, 1], [2, 3], [4]]
[43] pry(main)> array.each_with_object([]) { |e, a| e.each_index { |i| a[i] = a[i].to_i + e[i] } }
=> [7, 4, 1]

file4.txt

class Array
  def safe_transpose
    result = []
    max_size = self.max { |a,b| a.size <=> b.size }.size
    max_size.times do |i|
      result[i] = Array.new(self.first.size)
      self.each_with_index { |r,j| result[i][j] = r[i] }
    end
    result
  end
end

file5.txt

[15] pry(main)> [[1,1,1],[2,3],[4]].safe_transpose.map{|ary|ary.inject(){|s,i|s=s+i.to_i}}
=> [7, 4, 1]

file6.txt

[16] pry(main)> [[1,1,1],[2,3],[4]].transpose
IndexError: element size differs (2 should be 3)

file7.txt

class Array
  def safe_transpose
    result = []
    max_size = self.max { |a,b| a.size <=> b.size }.size
    max_size.times do |i|
      result[i] = Array.new(self.first.size)
      self.each_with_index { |r,j| result[i][j] = r[i] }
    end
    result
  end
end

file8.txt

[14] pry(main)> [[1,1,1],[2,3],[4]].safe_transpose
=> [[1, 2, 4], [1, 3, nil], [1, nil, nil]]

file9.txt

[17] pry(main)> [[1,1,1],[2,3],[4]].safe_transpose.map{|ary|ary.inject(){|s,i|s=s+i.to_i}}
=> [7, 4, 1]