数组是否包含来自另一个数组的任何值? [英] Array include any value from another array?

问题描述

测试数组是否包含第二个数组中的任何元素的最有效方法是什么?

What's the most efficient way to test if an array contains any element from a second array?

下面的两个示例试图回答这个问题，foods是否包含cheeses中的任何元素:

Two examples below, attempting to answer the question does foods contain any element from cheeses:

cheeses = %w(chedder stilton brie mozzarella feta haloumi reblochon)
foods = %w(pizza feta foods bread biscuits yoghurt bacon)

puts cheeses.collect{|c| foods.include?(c)}.include?(true)

puts (cheeses - foods).size < cheeses.size

推荐答案

(cheeses & foods).empty?

正如Marc-AndréLafortune在评论中说的那样，&在线性时间内起作用，而any? + include?将是平方的.对于更大的数据集，线性时间会更快.对于小型数据集，如Lee Jarvis的回答所示，any? + include?可能更快-可能是因为&分配了一个新的Array，而另一种解决方案却没有，并且它只是一个简单的嵌套循环以返回布尔值.

As Marc-André Lafortune said in comments, & works in linear time while any? + include? will be quadratic. For larger sets of data, linear time will be faster. For small data sets, any? + include? may be faster as shown by Lee Jarvis' answer -- probably because & allocates a new Array while another solution does not and works as a simple nested loop to return a boolean.

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