如何創建基於索引的使用Ruby數組的數組的數組的一個子集

Question

如果我有一個這樣的數組：

[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20] 

，我想選擇基於該數組的一個子集索引的該任意數組：

[0,1,4,7,8,13,14,15,18,19] 

其結果是所述第一陣列的這個子集：

[1,2,5,8,9,14,15,16,19,20] 

我的問題是，我如何從索引數組中創建一個簡單的函數（1或2行）並獲取子集的起始數組？

Answer 1

arr = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20] 
indexes = [0,1,4,7,8,13,14,15,18,19] 

arr.values_at(*indexes) # => [1, 2, 5, 8, 9, 14, 15, 16, 19, 20] 

Answer 2

arr = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20] 
index = [0,1,4,7,8,13,14,15,18,19] 
arr.select.with_index{|m,i| m if index.include? i} 
#=> [1, 2, 5, 8, 9, 14, 15, 16, 19, 20] 

Answer 3

arr = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20] 
index = [0,1,4,7,8,13,14,15,18,19] 

arr.each_with_index {|value,index| p value if indexes.include?(index)}