Ruby 中的 MapReduce 数组

Question

我有两个这样的数组：

["1","7","8","10"]

和

["1","2","3","6","9","11"]

Place这些数组代表用户选择的一个类的 id 。我想选择得票最多的地点 id。我尝试过transpose，但由于数组大小不同，因此无法转置。

此示例的预期输出是：

{ "1" => 2, "7" => 1, "8" => 1, "10" => 1, "2" => 1, "3" => 1, "6" => 1, "9" => 1, "11" => 1 }

Answer 1

您可以连接所有数组并计算相同元素的数量，如下所示：

arrays = [["1","7","8","10"], ["1","2","3","6","9","11"]].reduce(:+)
arrays.inject(Hash.new(0)) { |memo, e| memo.update(e => memo[e] + 1) }
# "{ "1" => 2, "7" => 1, "8" => 1, "10" => 1, "2" => 1, "3" => 1, "6" => 1, "9" => 1, "11" => 1 }"

一旦获得中间结果，就可以max_by从哈希中选择具有最大值的键：

arrays = [["1","7","8","10"], ["1","2","3","6","9","11"]].reduce(:+)
arrays.inject(Hash.new(0)) { |memo, e| memo.update(e => memo[e] + 1) }
      .max_by { |_, count| count }[0]
#=> "1"