[1,2,3,3] - [1,2,3] produces the empty array []. Is it possible to retain duplicates so it returns [3]?
[1,2,3,3] - [1,2,3]产生空数组[]。是否可以保留重复项以便返回[3]?
3 个解决方案
#1
3
I am so glad you asked. I would like to see such a method added to the class Array in some future version of Ruby, as I have found many uses for it:
你问我很高兴。我希望在未来的Ruby版本中看到这样的方法添加到类Array中,因为我发现它有很多用途:
class Array def difference(other) cpy = dup other.each do |e| ndx = cpy.rindex(e) cpy.delete_at(ndx) if ndx end cpy endendA description of the method and links to some of its applications are given here.
这里给出了该方法的描述和它的一些应用的链接。
By way of example:
举例来说:
a = [1,2,3,4,3,2,4,2]b = [2,3,4,4,4]a - b #=> [1]a.difference b #=> [1,2,3,2]#2
1
As far as I know, you can't do this with a built-in operation. Can't see anything in the ruby docs either. Simplest way to do this would be to extend the array class like this:
据我所知,你不能通过内置操作来做到这一点。在ruby文档中也看不到任何内容。最简单的方法是扩展数组类,如下所示:
class Array def difference(array2) final_array = [] self.each do |item| if array2.include?(item) array2.delete_at(array2.find_index(item)) else final_array << item end end endendFor all I know there's a more efficient way to do this, also
据我所知,还有一种更有效的方法
#3
0
EDIT:As suggested by user2864740 in question comments, using Array#slice! is a much more elegant solution
编辑:正如user2864740在问题评论中所建议的,使用Array#slice!是一个更优雅的解决方案
def arr_sub(a,b) a = a.dup #if you want to preserve the original array b.each {|del| a.slice!(a.index(del)) if a.include?(del) } return aendMy original answer
我原来的答案
def arr_sub(a,b) b = b.each_with_object(Hash.new(0)){ |v,h| h[v] += 1 } a = a.each_with_object([]) do |v, arr| arr << v if b[v] < 1 b[v] -= 1 endendarr_sub([1,2,3,3],[1,2,3]) # a => [3]arr_sub([1,2,3,3,4,4,4],[1,2,3,4,4]) # => [3, 4]arr_sub([4,4,4,5,5,5,5],[4,4,5,5,5,5,6,6]) # => [4]#1
3
I am so glad you asked. I would like to see such a method added to the class Array in some future version of Ruby, as I have found many uses for it:
你问我很高兴。我希望在未来的Ruby版本中看到这样的方法添加到类Array中,因为我发现它有很多用途:
class Array def difference(other) cpy = dup other.each do |e| ndx = cpy.rindex(e) cpy.delete_at(ndx) if ndx end cpy endendA description of the method and links to some of its applications are given here.
这里给出了该方法的描述和它的一些应用的链接。
By way of example:
举例来说:
a = [1,2,3,4,3,2,4,2]b = [2,3,4,4,4]a - b #=> [1]a.difference b #=> [1,2,3,2]#2
1
As far as I know, you can't do this with a built-in operation. Can't see anything in the ruby docs either. Simplest way to do this would be to extend the array class like this:
据我所知,你不能通过内置操作来做到这一点。在ruby文档中也看不到任何内容。最简单的方法是扩展数组类,如下所示:
class Array def difference(array2) final_array = [] self.each do |item| if array2.include?(item) array2.delete_at(array2.find_index(item)) else final_array << item end end endendFor all I know there's a more efficient way to do this, also
据我所知,还有一种更有效的方法
#3
0
EDIT:As suggested by user2864740 in question comments, using Array#slice! is a much more elegant solution
编辑:正如user2864740在问题评论中所建议的,使用Array#slice!是一个更优雅的解决方案
def arr_sub(a,b) a = a.dup #if you want to preserve the original array b.each {|del| a.slice!(a.index(del)) if a.include?(del) } return aendMy original answer
我原来的答案
def arr_sub(a,b) b = b.each_with_object(Hash.new(0)){ |v,h| h[v] += 1 } a = a.each_with_object([]) do |v, arr| arr << v if b[v] < 1 b[v] -= 1 endendarr_sub([1,2,3,3],[1,2,3]) # a => [3]arr_sub([1,2,3,3,4,4,4],[1,2,3,4,4]) # => [3, 4]arr_sub([4,4,4,5,5,5,5],[4,4,5,5,5,5,6,6]) # => [4]