如何在多维数组中聚合某些数组？
如何在多维数组中聚合某些数组？
提问于 2019-07-12 02:22:46
我有一个嵌套的数组，需要按照下面所示的方式聚合除了最后一个元素之外相等的内部数组。
_array = [["Nokia","Review","3"], ["Nokia","Review","2"],
["Samsung","Review","4"], ["Apple","Review","4"],
["Apple","Review","3"]]所需输出：
[["Nokia","Review","5"], ["Samsung","Review","4"], ["Apple","Review","7"]]回答 2
Stack Overflow用户
回答已采纳
发布于 2019-07-12 02:37:06
一行代码，只是为了好玩：
_array.group_by{ |e| e.first(2) }
.transform_values { |v| v.sum { |e| e.last.to_i } }
.map { |k, v| k << v.to_s }
#=> [["Nokia", "Review", 5], ["Samsung", "Review", 4], ["Apple", "Review", 7]]
一些帮助理解的步骤
_array.group_by{ |e| e.first(2) }
#=> {["Nokia", "Review"]=>[["Nokia", "Review", "3"],["Nokia", "Review", "2"]],
# ["Samsung", "Review"]=>[["Samsung", "Review", "4"]],
# ["Apple", "Review"]=>[["Apple", "Review", "4"], ["Apple", "Review", "3"]]}
_array.group_by{ |e| e.first(2) }.transform_values { |v| v.sum { |e| e.last.to_i } }
#=> {["Nokia", "Review"]=>5, ["Samsung", "Review"]=>4, ["Apple", "Review"]=>7}然后是map。
Stack Overflow用户
发布于 2019-07-12 02:29:50
这是一个非常奇怪的形式，因为数字是字符串，但您可以通过一些转换进行累积：
array = [["Nokia","Review","3"], ["Nokia","Review","2"], ["Samsung","Review","4"], ["Apple","Review","4"], ["Apple","Review","3"]]
# Define a tabulator Hash defaulting to count of 0
array.each_with_object(Hash.new(0)) do |a,h|
# Use the first two elements of the array as the key
h[a[0,2]] += a[2].to_i
end.map do |k, v|
# Convert back to string value, combining key and count
k + [ v.to_s ]
end
# => [["Nokia", "Review", "5"], ["Samsung", "Review", "4"], ["Apple", "Review", "7"]]正如您所看到的，如果数据是不同的形式，或者即使数字实际上是整数，这将会容易得多。
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原文链接：
https://stackoverflow.com/questions/56995257
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