基于排序值数组排序哈希数组 [英] Sorting an Array of hashes based on an Array of sorted values

问题描述

  user_quizzes = [{：id => 3897，：quiz_id => 1793，：user_id => 252}，{：id => 3897，：quiz_id => 1793，：user_id => 475}，{：id => 3897，：quiz_id => 1793，：user_id => 880}，{：id => 3897，：quiz_id => 1793，：user_id => 881}，{：id => 3897，：quiz_id => 1793，：user_id => 882}，{：id => 3897，：quiz_id => 1793，：user_id => 883}，{：id => 3897，：quiz_id => 1793，：user_id => 884}] 
  

另外，基于特定的条件，我将' user_id 'key from同一个散列并对它进行排序，并在下面给出相同的数组：

  sorted_user_ids = [880,881,882,883,884,475,252] 
  

现在，我需要 user_quizzes 将根据 sorted_user_ids user_id 顺序进行重新排列c>数组。

任何人都可以帮助我解决这个问题。 ：）

解决方案

使用 Enumerable＃sort_by 或 Array＃sort_by！ ，您可以指定将用于比较的密钥：

  user_quizzes = [
 {：id => 3897，：quiz_id => 1793，：user_id => 252}，
 {：id => 3897，：quiz_id => 1793，：user_id => 475}，
 {：id => 3897，：quiz_id => 1793，：user_id => 880}，
 {：id => 3897，：quiz_id => 1793，：user_id => 881}，
 {：id => 3897，：quiz_id => 1793，：user_id => 882}，
 {：id => 3897，：quiz_id => 1793，：user_id => 883}，
 {：id => 3897，：quiz_id => 1793，：user_id => 884} 
] 
 sorted_user_ids = [880，881，882，883，884，475，252] 
 user_quizzes.sort_by {| x | sorted_user_ids.index（x [：user_id]）} 
＃=> [{：id => 3897，：quiz_id => 1793，：user_id => 880}，
＃{：id => 3897，：quiz_id => 1793，：user_id => 881 }，
＃{：id => 3897，：quiz_id => 1793，：user_id => 882}，
＃{：id => 3897，：quiz_id => 1793， ：user_id => 883}，
＃{：id => 3897，：quiz_id => 1793，：user_id => 884}，
＃{：id => 3897，： quiz_id => 1793，：user_id => 475}，
＃{：id => 3897，：quiz_id => 1793，：user_id => 252}] 
  

附注： sorted_user_ids.index（x [：user_id]）可能会成为瓶颈（重复O（n）操作），如果数组很大。

构建一个映射 user_id s在这种情况下的订单：

  sorted_user_ids = [880，881，882，883，884，475，252] 
 order = Hash [sorted_user_ids.each_with_index.to_a] 
＃=> {880 => 0,881 => 1,882 => 2,883 => 3,884 => 4,475 => 5,252 => 6} 
 user_quizzes.sort_by {| x | order [x [：user_id]]} 
＃=>同上。 
  

I have an array of hashes as given below:

user_quizzes = [{:id => 3897, :quiz_id => 1793, :user_id => 252}, {:id => 3897, :quiz_id => 1793, :user_id => 475}, {:id => 3897, :quiz_id => 1793, :user_id => 880}, {:id => 3897, :quiz_id => 1793, :user_id => 881}, {:id => 3897, :quiz_id => 1793, :user_id => 882}, {:id => 3897, :quiz_id => 1793, :user_id => 883}, {:id => 3897, :quiz_id => 1793, :user_id => 884}]

Also, based on a particular condition I took the values of 'user_id' key from the same hash and sorted it and the same array is given below:

sorted_user_ids = [880, 881, 882, 883, 884, 475, 252]

Now, I need the user_quizzes to be rearranged based on the order of user_id in sorted_user_ids array.

Can anyone please help me on this. :)

解决方案

Using Enumerable#sort_by or Array#sort_by!, you can specify the key that will be used for comparison:

user_quizzes = [
  {:id => 3897, :quiz_id => 1793, :user_id => 252},
  {:id => 3897, :quiz_id => 1793, :user_id => 475},
  {:id => 3897, :quiz_id => 1793, :user_id => 880},
  {:id => 3897, :quiz_id => 1793, :user_id => 881},
  {:id => 3897, :quiz_id => 1793, :user_id => 882},
  {:id => 3897, :quiz_id => 1793, :user_id => 883},
  {:id => 3897, :quiz_id => 1793, :user_id => 884}
]
sorted_user_ids = [880, 881, 882, 883, 884, 475, 252]
user_quizzes.sort_by { |x| sorted_user_ids.index(x[:user_id]) }
# => [{:id=>3897, :quiz_id=>1793, :user_id=>880},
#     {:id=>3897, :quiz_id=>1793, :user_id=>881},
#     {:id=>3897, :quiz_id=>1793, :user_id=>882},
#     {:id=>3897, :quiz_id=>1793, :user_id=>883},
#     {:id=>3897, :quiz_id=>1793, :user_id=>884},
#     {:id=>3897, :quiz_id=>1793, :user_id=>475},
#     {:id=>3897, :quiz_id=>1793, :user_id=>252}]

Side note: sorted_user_ids.index(x[:user_id]) can become bottleneck (repeat O(n) operations), if the array is huge.

Build a hash that maps user_ids to orders in such case:

sorted_user_ids = [880, 881, 882, 883, 884, 475, 252]
order = Hash[sorted_user_ids.each_with_index.to_a]
# => {880=>0, 881=>1, 882=>2, 883=>3, 884=>4, 475=>5, 252=>6}
user_quizzes.sort_by { |x| order[x[:user_id]] }
# => same as above.

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