重构:循环从嵌套数组中检索元素
重构:循环从嵌套数组中检索元素
提问于 2016-01-05 16:19:38
我需要检查一个散列数组，每个散列包含一个标签和一个数据数组。最终结果将是一个连接的字符串，首先是label，然后是对应于该标签的数据。
散列的输入数组如下所示：
[{label: "first", data: [1, 2]}, {label: "second", data: [3, 4, 5]}, {label: "third", data: []}, {label: "fourth", data: [6]}]
在这个例子中，max_returns应该是很高的，比如：10
def round_robin(arr, max_returns)
result = ''
i = 0 # number of grabbed elements
j = 0 # inner array position
k = 0 # outer array position
l = 0 # number of times inner array length has been exceeded
while i < max_returns do
if k >= arr.length
j += 1
k = 0
end
element = arr[k]
if element[:data].empty?
k += 1
next
end
if j >= element[:data].length
l += 1
k += 1
if l > arr.length && i < max_returns
break
end
next
end
result += element[:label] + ': ' + element[:data][j].to_s + ', '
i += 1
k += 1
end
result
end根据上述投入，产出应是：
"first: 1, second: 3, fourth: 6, first: 2, second: 4, second: 5"
另外：max_returns是检索结果总数的最大数目。因此，如果我的示例有一个max_returns = 3，那么输出应该是：
"first: 1, second: 3, fourth: 6"
问题：是否有更好或更有效的方法从多个数组中以循环方式获取数据？
回答 5
Stack Overflow用户
回答已采纳
发布于 2016-01-05 22:58:25
这样做是可行的：
arr = [{ label: "first", data: [1, 3] },
{ label: "second", data: [3, 4, 5] },
{ label: "third", data: [] },
{ label: "fourth", data: [6] }]
results = []
arr.each do |h|
h[:data].each_with_index do |d, i|
results[i] ||= []
results[i] << "#{h[:label]}: #{d}"
end
end
results.flatten.join(', ')
#=> "first: 1, second: 3, fourth: 6, first: 3, second: 4, second: 5"Stack Overflow用户
发布于 2016-01-05 16:53:35
▶ input = [{label: "first", data: [1, 2]},
{label: "second", data: [3, 4, 5]},
{label: "third", data: []},
{label: "fourth", data: [6]}]
▶ max = input.max_by { |e| e[:data].size }[:data].size
▶ input.map do |h|
[[h[:label]] * max].flatten.zip h[:data] # make it N×M (for transpose)
end.transpose.map do |e|
e.reject { |_, v| v.nil? } # remove nils
end.flatten(1).map { |e| e.join ': ' }.join ', '
#⇒ "first: 1, second: 3, fourth: 6, first: 2, second: 4, second: 5"如果没有最后两个联接，结果将是一个数组数组：
#⇒ [["first", 1], ["second", 3], ["fourth", 6],
# ["first", 2], ["second", 4], ["second", 5]]Stack Overflow用户
发布于 2016-01-05 18:16:39
arr = [{ label: "first", data: [1, 2] },
{ label: "second", data: [3, 4, 5] },
{ label: "third", data: [] },
{ label: "fourth", data: [6] }]
labels, data = arr.map { |h| [h[:label], h[:data].dup] }.transpose
#=> [["first", "second", "third", "fourth"], [[1, 2], [3, 4, 5], [], [6]]]
data.map(&:size).max.times.with_object([]) do |_,arr|
labels.each_index do |i|
d = data[i].shift
arr << "#{labels[i]}: #{d}" if d
end
end.join(', ')
#=> "first: 1, second: 3, fourth: 6, first: 2, second: 4, second: 5" 页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/34616351
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