提取從數組（距離誤差的差值）的重複元素

Question

我想提取/獲取所有標籤之間的元素和「：/ DESC」此數組

array = ["hello", ":desc:", "claire", "et", "concise", ":/desc:", 
     ":desc:", "claire", "caca", "concise", "test", ":/desc:"] 

讓我「：DESC」有

new_array = [[":desc:", "claire", "et", "concise", ":/desc:"], 
      [":desc:", "claire", "caca", "concise", "test", ":/desc:"]] 

我試圖

final_array = [] 

start_element = ':desc:' 
end_element = ':/desc:' 

while array.any? 
    final_array << array.slice! 
(array.find_index(start_element)..array.find_index(end_element)) 
end 

但它顯然不工作，因爲我得到一個bad value for range錯誤。

Answer 1

這裏有幾個問題。從您的示例數組中看起來像結尾元素是':/desc'而不是':/desc:'（即沒有結尾:）。儘管如此，這可能只是一個錯字。

的主要問題是，除去2片後，陣列將不會是空的（它仍將包含從第一start_element前"hello"。這意味着array.any?條件仍然會當find_index(start_element)不會真找到匹配的元素在這種情況下find_index將返回nil，欲以slice!時導致no implicit conversion from nil to integer

如果你知道你的數據將始終包含start_element和end_element在配對再一個辦法是：。

while start_index = array.find_index(start_element) 
    end_index = array.find_index(end_element) 
    final_array << array.slice!(start_index..end_index) 
end 

---

當遇到這種類型的錯誤在未來，一些值得信賴的puts調試會有幫助，在這種情況下檢查2個索引和數組的剩餘內容：

while array.any? 
    start_index = array.find_index(start_element) 
    end_index = array.find_index(end_element) 
    puts "#{start_index}..#{end_index}" 
    final_array << array.slice!(start_index..end_index) 
    puts array.inspect 
end 

1..5 
["hello", ":desc:", "claire", "caca", "concise", "test", ":/desc"] 
1..6 
["hello"] 
.. 
TypeError: no implicit conversion from nil to integer 
from (pry):146:in `slice!' 

Answer 2

也可以使用的Enumarable#slice_after和Enumarable#drop_while組合：

array.slice_after(':/desc').map { |e| e.drop_while { |i| i != ':desc:' } } 
#=> [[":desc:", "claire", "et", "concise", ":/desc"], 
# [":desc:", "claire", "caca", "concise", "test", ":/desc"]] 

Answer 3

我認爲開始與子陣並以":/desc"結尾，並且不包含":/desc"的其他實例。請注意，如果返回arr = [":desc:", ":desc:", ":/desc"],[a]。我對數組的結構沒有任何假設（但我沒有測試過所有的可能性）。如果做出某些假設（存在匹配的非重疊對，例如簡化是可能的。

代碼

def extract(arr, target_start, target_end) 
    arr.select { |s| (s == target_start)..(s == target_end) ? true : false }. 
     slice_when { |s,t| [s, t] == [target_end, target_start] }. 
     to_a. 
     tap { |a| a.pop unless a.last.last == target_end } 
end 

例子

target_start = ":desc:" 
target_end = ":/desc" 

arr = ["hello", ":desc:", "claire", "et", "concise", ":/desc", 
     ":desc:", "claire", "caca", "concise", "test", ":/desc"] 
extract(arr, target_start, target_end) 
    #=> [[":desc:", "claire", "et", "concise", ":/desc"], 
    # [":desc:", "claire", "caca", "concise", "test", ":/desc"]] 

arr = ["hello", ":desc:", "claire", "et", "concise", ":/desc", "wanda", 
     ":desc:", "claire", "caca", "concise", "test", ":/desc", "herb"] 
extract(arr, target_start, target_end) 
    # => [[":desc:", "claire", "et", "concise", ":/desc"], 
    #  [":desc:", "claire", "caca", "concise", "test", ":/desc"]] 

arr = ["hello", ":desc:", "claire", "et", "concise", ":/desc", 
     ":desc:", "claire", "caca", "concise", "test"] 
extract(arr, target_start, target_end) 
    #=> [[":desc:", "claire", "et", "concise", ":/desc"]] 

arr = ["hello", ":desc:", "claire", "et", "concise", ":desc:", "claire", 
     "caca", "concise", "test"] 
extract(arr, target_start, target_end) 
    #=> [] 

說明

考慮

arr = ["hello", ":desc:", "claire", "et", "concise", ":/desc", 
     ":desc:", "claire", "caca", "concise", "test"] 

和target_start和target_end如在示例中給出的。步驟如下。

b = arr.select { |s| (s == target_start)..(s == target_end) ? true : false } 
    #=> [":desc:", "claire", "et", "concise", ":/desc", ":desc:", "claire", 
    # "caca", "concise", "test"] 

該第一步驟，其利用Ruby的flip-flop operator的，返回包含除那些先於第一":desc:"和arr所有元素那些每個":/desc"和跟隨第一":desc:"之間的陣列。

接下來我們使用Enumerable#slice_when（Ruby v2.2中的新增功能）來生成根據需要切片b的枚舉器，然後將該枚舉器轉換爲數組。

c = b.slice_when { |s,t| [s, t] == [target_end, target_start] } 
    #=> #<Enumerator: #<Enumerator::Generator:0x00000001dd4f18>:each> 
d = c.to_a 
    #=> [[":desc:", "claire", "et", "concise", ":/desc"], 
    # [":desc:", "claire", "caca", "concise", "test"]] 

的最後一步是去除d最後一個數組，如果它不與":/desc"，這是這裏的情況下終止。我們可以使用，但不能直接返回彈出的元素，這也會導致該方法返回該值。但是，如果我們在Object#tap塊中使用它，一切都很好。

d.tap { |a| a.pop unless a.last.last == target_end } 
    #=> [[":desc:", "claire", "et", "concise", ":/desc"]]