填充稀疏数组

Range.new(*rare.transpose.first.sort.values_at(0,-1)).inject([]){|a,i|
  a<<[i, Hash[rare][i] || a.last.last]
}

逐步说明:

1. rare.transpose.first.sort.values_at(0,-1) 查找最小值和最大值 x ( [0,7] 在您的示例中)
2. Range.new() 超出范围( 0..7 )
3. inject 循环访问范围和 X 返回对 [x,y] ,在哪里 y 是:
   1. Y 来自输入数组,其中定义了
   2. Y 从先前评估的对中,其中

注:以下是求最小值和最大值x的其他方法:

[:min,:max].map{|m| Hash[rare].keys.send m}
rare.map{|el| el.first}.minmax # Ruby 1.9, by steenslag

rare = [[0,1], [2,3], [4,5], [7,8]]

filled = rare.inject([]) do |filled, point|
  extras = if filled.empty?
             []
           else
             (filled.last[0] + 1 ... point[0]).collect do |x|
               [x, filled.last[1]]
             end
           end
  filled + extras + [point]
end

p filled
# => [[0, 1], [1, 1], [2, 3], [3, 3], [4, 5], [5, 5], [6, 5], [7, 8]]

安 inject 解决方案:

filled = rare.inject([]) do |filled_acc, (pair_x, pair_y)|
  padded_pairs = unless filled_acc.empty?    
    last_x, last_y = filled_acc.last
    (last_x+1...pair_x).map { |x| [x, last_y] }
  end || []
  filled_acc + padded_pairs + [[pair_x, pair_y]] 
end

更多关于 Enumerable#inject 和Ruby函数编程 here .

irb(main):001:0> rare = [[0,1], [2,3], [4,5], [7,8]]
=> [[0, 1], [2, 3], [4, 5], [7, 8]]
irb(main):002:0> r=rare.transpose
=> [[0, 2, 4, 7], [1, 3, 5, 8]]
irb(main):003:0> iv = (r[0][0]..r[0][-1]).to_a.select {|w| !r[0].include?(w) }
=> [1, 3, 5, 6]
irb(main):004:0> r[1][-1]=r[1][-2]
=> 5
irb(main):005:0> p (iv.zip(r[1]) + rare).sort
[[0, 1], [1, 1], [2, 3], [3, 3], [4, 5], [5, 5], [6, 5], [7, 8]]
=> [[0, 1], [1, 1], [2, 3], [3, 3], [4, 5], [5, 5], [6, 5], [7, 8]]